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CHEMISTRY 


FOR 

PHOTOGRAPHERS. 

BY 

CHAS.  F.  TOWNSEND,  F.C.S.,  F.R.P.S. 


ILL  USTRA  LED. 


I B 


NEW  YORK ; 

SPON  & CHAMBERLAIN.  12  CORTLANDT  ST 


CONTENTS. 


CHAP.  PAGF. 

I.  Introduction . . ‘5 

II.  Chemistry  Generally,  and  the  Chemistry  of 

THE  Silver  Salts  in  particular,  ...  13 

III.  The  Chemistry  of  the  Photographic  Image,  . 36 

IV.  Developers, 53 

V.  Reversal, 79 

VI.  Reduction,  Intensification,  &c.,  ...  83 

VII.  Printing  in  Silver 88 

VIII.  Printing  in  Salts  of  Iron,  . ...  102 

IX.  Printing  in  Platinum,  .....  105 

X.  The  Bichromate  Printing  Processes,  . . 109 

XI.  Orthochromatism,  ......  115 

XII.  Impurities  and  Substances  that  Alter  in 

the  Air,  ........  118 

XIII.  Recovery  of  Residues,  .....  123 

XIV.  Cellulose,  . . , 125 

XV.  Resins,  Varnishes,  &c., 129 

Cyclopedic  Index, 140 


CHEMISTRY  FOR  PHOTOGRAPHERS. 


CHAPTEE  I. 

Introductory. 

- The  first  essentials  to  anyone  studying  chemistry 
are  accuracy  and  cleanliness.  Most  of  the  surpris- 
ing results  obtained  by  students  in  their  early  days 
are  due  to  want  of  cleanliness.  Another  point  I 
should  like  to  impress  upon  those  just  taking  up  the 
subject  is  that  learning  “ facts  ” in  a more  or  less 
mechanical  way  is  not  learning  chemistry.  It  is 
said  that  a good  lawyer  does  not  know  much  law, 
but  knows  where  to  find  his  law.  The  same  applies 
to  a good  chemist.  Above  all,  endeavour  to  get  an 
insight  into  the  nature  of  things,  and  remember  that 
the  proper  place  for  a dictionary  is  not  inside  a 
man’s  head,  but  on  a shelf.  If  particular  sets  of 
facts  or  figures  are  often  required  for  reference, 
don’t  try  to  learn  them,  but  cut  or  copy  them  out, 
give  them  a coat  of  varnish  and  paste  them  on  the 


6 


PRELIMINARY  HINTS. 


work-room  door.  There  is  still  another  point : never 
take  for  granted  any  statement  you  read  if  you  pos- 
sess the  means  of  testing  it  and  have  five  minutes 
to  spare.  Even  if  the  statement  is  correct,  more 
knowledge  will  be  gained  by  merely  seeing  the  thing 


V 


V 

Fig.  1. 

happen  than  by  reading  about  it  all  day.  Statements 
in  photographic  and  other  scientific  books  are  fre- 
quently incorrect,  having  crept  into  an  early  text- 
book by  mistake  and  been  copied  religiously  ever 
since.  Mistakes  have  a way  of  creeping  into  a book, 


MEASUKING  APPARATUS. 


7 


however  carefully  it  is  written,  so  test  all  statements 
when  an  opportunity  occurs. 

As  all  chemical  and  photographic  work  is  based 
on  measurement,  it  is  important  to  have  a rational 
system  of  weights  and  measures.  For  this  reason 
it  would  be  well  if  every  photographer  discarded  the 


XI  - i\ 


Fig.  2. 

system  of  the  pharmacist,  together  with  his  measur- 
ing apparatus,  replacing  ounces  and  minims  by 
grams  and  cubic  centimetres,  and  conical  graduates 
by  burettes  and  pipettes.  The  conical  measures 
now  in  use  are  bad  in  every  way : it  is  practically 
impossible  to  measure  accurately  with  them,  and 
they  are  very  difficult  to  keep  clean. 


8 BURETTES  AND  PIPETTES. 

The  construction  of  a burette  will  readily  be  seen 
from  the  figure  (fig.  1).  The  instrument  can  be 
purchased  with  a glass  tap,  or  with  a glass  jet,  a 
piece  of  india-rubber  tubing  and  a pinchcock,  the 
latter  being  quite  as  convenient  and  much  cheaper. 
For  photographic  purposes,  burettes  for  the  different 
developing  solutions  should  be  suspended  round  the 
sink  as  shown  in  the  sketch  (fig.  2),  being  fed  from 
stock  bottles  on  a shelf  above,  when  large  quantities 
of  material  are  used.  It  is  well  to  have  an  opal 
glass  plate  at  the  back  of  the  fixed  burette,  and  to 
read  the  level  of  the  bottom  of  the  black  curve  at 
the  top  of  the  liquid  when  measuring.  A float  with 
a line  engraved  on  it  is  sometimes  used  for  reading, 
and  has  the  advantage  of  keeping  the  solution  from 
the  air  as  well  as  or  better  than  a stopper.  The 
construction  of  a pipette  will  be  seen  from  the 
last  part  of  figure  1.  It  is  filled  by  drawing  up  the 
liquid  with  the  mouth : the  finger  is  then  placed 
rapidly  on  the  top,  and  the  liquid  is  allowed  to  run 
down  to  the  mark.  The  pipette  with  its  contents 
is  then  transferred  bodily  to  the  vessel,  into  which 
it  is  required  to  run  the  liquid. 

In  the  metric  system,  the  centimetre  is  the 
measure  of  length,  the  cubic  centimetre  the  measure 
of  capacity,  and  the  weight  of  1 cubic  centimetre 
of  water  at  15°  C.,  or  the  gram,  is  the  measure  of 
weight.  How  delightfully  simple  these  are,  com- 
pared to  the  complicated  and  heterogeneous  measures 
of  the  pharmacist ! An  inch  is  about  centi- 


WEIGHTS  AND  MEASURES. 


9 


metres,  and  an  ounce  about  28  grams,  a fluid  ounce 
being  28  cubic  centimetres.  For  larger  measures 
the  litre  containing  1000  c.c.,  and  the  kilogramme  or 
kilo,  of  1000  grams,  are  used.  For  small  measures 
the  decimals  of  the  gram  and  the  centimetre  are 
employed.  Going  up  the  scale,  10,  100,  1000,  etc., 
grams  and  centimetres  follow  in  order,  and  going 
down  the  scale  -jL,  yoVo  ^ gram  or  centi- 
metre follow  one  another,  the  decimal  system  being 
employed  throughout.  It  is  convenient  to  remember 
that  a litre  is  very  nearly  a pint  and  three-quarters. 
The  following  table  gives  the  means  of  converting 
English  into  metric  equivalents,  and  vice  versd. 


TABLE  I. — Weights  and  Measures  in  British  and 
Metric  Systems. 

APOTHECARIES’  WEIGHT  (by  which  Formul.®  are  made  up). 

20  grains  =:!  scrapie  . . = 1*296  grams. 

8 drachms  = 1 ounce  = 480  grains  ==  31 '1  ,, 

3 scruples  = 1 drachm  = 60  ,,  = 3*887  ,, 

12  ounces  = l pound  = 5760  ,,  =373*2  ,, 

AVOIRDUPOIS  WEIGHT  (by  which  Chemicals  are  sold). 

437|  grains  = 1 ounce  . . . = 28*4  grams. 

1 6 ounces  = 1 pound  = 7 000  grains  = 453  *59  , , 


METRIC  SYSTEM— WEIGHT. 

10  milligrams  = 1 centigram  . . . = *1543  grain. 

10  centigrams  = 1 decigram  = 100  milligrams  = 1*543  ,, 

10  decigrams  =1  gram  = 100  centigrams  = 15'432  ,, 

10  grams  =1  decagram  . . . =154*323  ,, 

10  decagrams  =1  hectogram  = 100  grams  . =3  ozs.  227|  grains. 

10  hectograms  = 1 kilogram  =1000  grams  . =35  ozs.  87^ 


10 


TEN  PER  CENT.  SOLUTIONS. 


MEASURES  OF  LENGTH. 

British. 

3 barley-corns  = 1 inch  . . = 2*54  cm. 

12  inches  . =1  foot  . . =30*48  ,, 

3 feet  . = 1 yard  = 36  inches  = 91*44  , , 

Metric. 

10  millimetres  = 1 centimetre  = *3937  inch  or  H approx. 

10  centimetres  = 1 decimetre  = 3’937  ,, 

10  decimetres  =1  metre  =39*37  ,, 

FLUID  MEASURE. 

1 drachm  . . . = 3 *5  cubic  centimetres. 

1 ounce  = 480  minims  = 28*4  ,,  ,, 

1 pound  =5760  „ =340*8  ,,  ,, 

1 pint*  . . . =568*0  ,,  ,, 

1 quart  = 40  ounces  = 1*136  litres. 

1 gallon  = 160  ,,  = 4*544  „ 

METRIC  SYSTEM— FLUID. 

1 cubic  centimetre  (c.c.)  . . . = 17  minims. 

10  ,,  ,,  =1  centilitre  . . =170  ,, 

10  ,,  centilitres  =1  decilitre  = 100  c.c.  = 3*52  fl.  oz. 

10  ,,  decilitres  =1  litre  =1000  c.c.  = 35*2  ,, 

* The  American  pint  is  16  ounces. 

Many  photographers  have  realised  the  con- 
venience of  a rational  system,  and  in  addition  to 
discarding  the  aboriginal  system  of  weights  and 
measures  have  adopted  ten  per  cent,  solutions  for 
all  their  work.  From  these  any  developer  or  other 
dilute  solution  can  be  made  up  in  a minimum  of 
time.  In  cases  of  stock  solutions  and  one  or  two 
other  instances  it  is  convenient  to  have  a fifty 
per  cent,  solution,  and  in  other  cases  five  per 
cent.,  or  perhaps  one  per  cent.,  solutions  must  be 
employed,  owing  to  the  difficulty  of  dissolving  a par- 


' 60  minims  = 
8 drachms  = 
12  ounces  = 
20  ounces  = 
2 pints  = 
4 quarts  = 


SCALES  OF  TEMPERATURE. 


11 


ticular  substance,  but  solutions  should  always  be 
made  up  to  contain  so  many  parts  per  cent. 

Some  confusion  in  the  reader’s  mind  may  be 
saved  by  pointing  out  again  that  a cubic  centimetre 
of  water  weighs  one  gram  and  a ten  per  cent,  solu- 
tion is  understood  to  mean  ten  grams  of  the  sub- 
stance in  one  hundred  of  water,  or  one  hundred 
grams  in  a litre,  i.e.,  ten  grams  dissolved  in  part  of 
the  water,  and  the  whole  made  up  to  an  even 
hundred,  not  to  a hundred  and  ten. 

Temperature  is  measured  in  this  country  by 
Fahrenheit’s  scale,  on  which  the  freezing  point  of 
water  is  32°,  and  the  boiling  point  212°,  zero  being 
32°  below  freezing  point.  In  the  Centigrade  or 
Celsius  scale  employed  in  scientific  work,  and  in 
general  practice  in  some  parts  of  the  continent,  the 
freezing  point  of  water  is  zero  and  the  boiling 
point  100°.  Table  II.  enables  you  to  convert  one 
scale  into  the  other. 

The  only  mathematical  signs  used  in  the  explana- 
tions will  be 

+ added  to 
- subtracted  from 
X multiplied  by 
-r  divided  by 
= equals 

and  the  signs  for  a proportion,  namely. 

As  is  to  so  is  to  the  figure  required, 

2 : 4 : : 3 : 

that  is  to  say. 


4x3~2  = G. 


12 


COMPAKISON  OF  THERMOMETERS. 


TABLE  1 1. — Thermometers.  Comparison  op 
Fahrenheit  and  Centigrade  (Celsius)  Scales. 


Cent. 

Fahr. 

Cent. 

Fahr. 

Cent. 

Fahr. 

100  B. 

212  B. 

65 

149 

30 

86 

99 

210*2 

64 

147*2 

29 

84*2 

98 

208*4 

63 

145*4 

28 

82*4 

97 

206*6 

62 

143*6 

27 

80*6 

96 

204*8 

61 

141-8 

26 

78*8 

95 

203 

60 

140 

25 

77 

94 

201*2 

59 

138-2 

24 

75*2 

93 

199*4 

58 

136*4 

23 

73*4 

92 

197*6 

57 

134*6 

22 

71*6 

91 

195*8 

56 

132*8 

21 

69*8 

90 

194 

55 

131 

20 

68 

89 

192*2 

54 

129*2 

19 

66*2 

88 

190*4 

53 

127*4 

18 

64*4 

87 

188-6 

52 

125*6 

17 

62*6 

86 

186*8 

51 

123*8 

16 

60*8 

85 

185 

50 

122 

15 

59 

84 

183*2 

49 

120*2 

14 

57*2 

83 

181*4 

48 

118*4 

13 

55*4 

82 

179-6 

47 

116*6 

12  ’ 

53*6 

81 

177*8 

46 

114*8 

11 

51*8 

80 

176 

45 

113 

10 

50 

79 

174*2 

44 

111*2 

9 

48*2 

78 

172*4 

43 

109*4 

8 

46*4 

77 

170*6 

42 

107*6 

7 

44*6 

76 

168*8 

41 

105*8 

6 

42*8 

75 

167 

40 

104 

5 

41 

74 

165*2 

39 

102*2 

4 

39*2 

73 

163*4 

38 

100*4 

3 

37*4 

72 

161*6 

37 

98*6 

2 

35*6 

71 

159*8 

36 

96*8 

1 

33*8 

70 

158 

35 

95 

Zero 

32 

69 

156*2 

34 

93-2 

68 

154*4 

33 

91*4 

67 

152*6 

32 

89*6 

66 

150*8 

31 

87*8 

DIRT. 


13 


CHAPTEK  IL 

Chemistry  generally,  and  the  Chemistry  of  the 
Silver  Salts  in  particular. 

At  the  beginning  of  the  book  mention  was  made 
of  the  importance  of  cleanliness.  “ Dirt  ” in  a 
chemical  sense  is  much  more  comprehensive  than 
is  usually  understood.  To  get  any  vessel  chemically 
clean  is  not  an  easy  process,  and  a vessel  after 
containing  most  chemicals  requires  several  careful 
washings  before  it  is  fit  for  use  again.  The  diffi- 
culty about  chemical  dirt  is  that  it  is  not  always 
visible  to  the  eye.  The  porcelain  dish  used  to  con- 
tain the  “ hypo  ” bath  may  look  beautifully  clean 
after  it  has  been  washed  out,  yet  the  porcelain  is 
probably  saturated  with  “ hypo  ” which  will  dissolve 
into  the  next  solution  placed  in  the  dish,  if  used 
for  anything  but  “hypo,”  and  spoil  all  the  plates 
and  paper  it  comes  into  contact  with.  Three  care- 
ful washings  are  generally  sufficient  to  cleanse  an 
article  thoroughly,  but  in  cases  where  very  careful 
cleansing  is  required,  such  as  plates  used  for  coating 
in  the  wet  plate  process,  a powerful  mixture,  such 
as  the  following,  must  be  employed,  which  burns  up 


14 


WASHING. 


any  dirt.  Never  allow  the  mixture  to  get  on  to 
clothes  or  fingers ! 

Potassium  bichromate,  . . 50  grams,  . 1 oz. 

Sulphuric  acid  (commercial),  . 50  c.c.,  . 1 „ 

Water,  ....  1000  c.c.,  . 20  ozs. 

Dissolve  the  bichromate  in  the  water,  and  when 
dissolved  add  the  sulphuric  acid  in  a thin  stream, 
stirring  the  while.  Por  some  purposes  it  is  con- 
venient to  use  much  more  sulphuric  acid. 

Einse  well  under  the  tap  when  clean.  The  solu- 
tion, if  no  water  is  added  to  it,  may  be  used  over 
and  over  again  until  exhausted. 

Perhaps  it  will  be  well  to  define  what  is  meant 
by  “ washing.”  In  regard  to  utensils  it  is  used  in 
the  ordinary  sense,  but  when  employed  in  connection 
with  prints  and  negatives  a wrong  impression  is 
often  conveyed.  When  a photographer  says  “ wash,” 
he  generally  means  “ soak.”  In  a recently  fixed 
negative,  for  example,  the  “ hypo  ” must  be  removed 
from  the  film  by  soaking  it  out.  A constant 
diffusion  goes  on  between  the  solution  of  “ hypo  ” 
in  the  film  and  the  clean  water  in  contact  with  it. 
At  first  this  diffusion  proceeds  very  rapidly,  and 
then  more  and  more  slowly  as  the  “ hypo  ” in  the 
film  becomes  dilute.  No  advantage  is  to  be  gained, 
therefore,  by  allowing  the  water  to  run  furiously 
over  the  surface  of  the  plate,  as  force  does  not 
assist  the  operation,  and  the  water  must  be  left  in 
contact  with  the  film  for  a sufficient  time  to  take  up 


ATOMS. 


15 


its  allowance  of  “ bypo.”  Eunning  water  is  a 
distinct  advantage,  although  frequent  changes  and 
rocking  of  the  dish  do  nearly  as  well,  but  the  water 
may  run  as  slowly  as  you  please,  and  should  how 
into  the  upper  part  of  the  whole  contents  of  the 
vessel,  but  out  from  the  lower  part.  A syphon 
should  be  used  to  remove  the  water  from  all  deep 
washing  tanks. 

Mention  will  be  made  directly  of  atoms  and 
molecules,  so  that  I had  better  explain  what  is 
meant  by  these  terms,  and  by  a chemical  element. 
If  pure  iron  is  ground  up  very  small  and  acted  upon 
by  the  strongest  forces  that  the  chemist  can  bring 
to  bear  upon  it,  nothing  but  iron  can  be  obtained 
from  it.  The  substance  cannot  be  split  up  into 
two  other  materials,  so  that  chemists  call  it  and 
all  such  substances  “ elements.”  If  the  powdered 
iron  that  was  spoken  of  just  now  be  examined 
under  the  microscope,  it  will  be  seen  that  the 
particles  would  bear  splitting  up  very  much  smaller. 
Chemists  have  come  to  the  conclusion,  that  if  human 
eyesight  and  fingers  were  keen  enough  to  go  on 
splitting  up  these  microscopic  particles,  a stage 
would  be  reached  when  the  particles  could  be  made 
no  smaller.  These  ultimate  particles  are  called 
“ atoms.”  All  the  atoms  of  iron,  for  instance,  may 
be  considered  as  being  exactly  alike  and  of  the 
same  size  and  weight.  As  it  is  not  possible  to 
examine  the  actual  atoms,  equal  quantities  of  the 
different  elements  are  compared  with  one  another. 


16 


CHEMICAL  ELEMENTS. 


In  this  way  it  is  found  that  the  iron  atom  is  56 
times  as  heavy  as  the  hydrogen  atom,  which,  being 
the  lightest,  is  called  1 and  is  used  as  the  standard 
of  atomic  weight.  The  silver  atom  is  108  times 
as  heavy  as  the  hydrogen  atom,  so  that  the  atomic 
weight  of  silver  is  108,  and  that  of  iron  56.  These 
atoms  combine  with  one  another  to  form  “ molecules,” 
so  that  a molecule  is  compounded  of  atoms.  The 
iron  atom,  for  instance,  may  combine  with  another 
iron  atom  to  form  an  iron  molecule,  or  it  may  com- 
bine with  one  or  more  atoms  of  some  other  element, 
such  as  chlorine  (see  later),  to  form  a molecule  of 
iron  chloride.  Now  I want  you  to  realise  that 
nothing  ever  happens  by  chance  in  chemistry. 
Similar  quantities  of  the  same  substances,  acting 
in  the  same  way,  always  produce  the  same  result, 
and  the  same  quantity  of  it,  as  you  will  see  directly. 

For  convenience,  chemists  employ  a kind  of 
shorthand,  using  symbols  for  the  different  sub- 
stances. H stands  for  hydrogen  and  for  1 gram  or 
ounce,  or  whatever  it  may  be,  of  hydrogen ; Fe 
(Latin,  ferrum)  stands  for  iron  and  for  56  grams, 
or  whatever  it  may  be,  of  iron,  and  so  on.  The 
following  symbols  for  different  elements  will  be 
used  in  this  chapter ; particulars  of  the  others  will 
be  found  in  the  index : — 


Atomic 


Hydrogen, 

Oxygen, 

Nitrogen, 


Name. 


Symbol.  Weight. 

. H 1 

. O 16 

. N 14 


WATER. 


17 


Sulphur, 

. S 

32 

Carbon,  .... 

. c 

12 

Chlorine, 

. Cl 

35*5 

Bromine, 

. Br 

80 

Iodine,  .... 

. I 

126-5 

Sodium, 

. Na 

23 

Potassium, 

. K 

39 

Silver,  .... 

. Ag 

108 

Coal  gas  is  a mixture  of  various  inflammable 
gaseous  materials,  but  amongst  them  contains  a 
large  proportion  of  a gas  called  hydrogen.  When 
this  burns,  it  combines  with  the  oxygen  in  the  air — 
another  gas — -to  form  water.  If  a cold  plate  or 
piece  of  metal  be  held  for  a second  or  two  over  a 
gas  flame  and  then  withdrawn,  the  surface  will  be 
coated  with  moisture  (the  soot  need  not  enter  into 
the  question).  It  has  been  found,  from  a large 
number  of  experiments,  that  a particle  of  water 
consists  of  two  atoms  of  hydrogen,  each  weighing  1, 
combined  with  one  atom  of  oxygen  weighing  16, 
and  is  represented  chemically  as  HOH  (or  HgO), 
the  total  weight  (1  + 16  + 1)  being  18. 

Sodium  is  a metal,  quite  soft  at  ordinary  tempera- 
tures, but  its  freshly  cut  surface  is  bright  and 
metallic  looking.  If  a piece  about  the  size  of  a 
large  pin’s  head  be  dropped  into  water,  a great 
commotion  ensues  and  bubbles  of  gas  are  given  off, 
which  take  Are  if  a light  is  applied  to  them,  and 
sometimes  do  so  on  their  own  account.  This  gas  is 
hydrogen.  The  atoms  of  sodium  (Na)  are  turning 

B 


18 


CAUSTIC  SODA. 


out  half  the  hydrogen  atoms  from  the  water, 
thus : — 

Water.  Sodium.  Caustic  Soda.  Hydrogen. 

HOH  + Na  = NaOH  + H escaping, 

added  to  forms  and 

Instead  of  water  there  is  now  a weak  solution  of 
caustic  soda,  which  turns  red  litmus -paper  blue, 
changes  acids  into  substances  that  are  not  acid  but 
neutral,  and  is  called  an  alkali.  If  more  sodium  be 
added  to  the  solution,  more  hydrogen  will  be  turned 
out,  the  alkaline  solution  becoming  stronger,  forming 
in  the  end  a solid  mass  of  caustic  soda,  which  could 
be  run  into  moulds  to  make  the  familiar  white 
sticks. 

It  has  been  shown  that  a particle  or  molecule,  as 
chemists  term  it,  of  water  (HOH)  weighs  18. 
In  caustic  soda  (HaOH)  there  is  an  atom  of 
sodium  (Na)  occupying  the  place  of  one  of  the  H’s, 
weighing  1.  How  an  atom  of  sodium  is  twenty- 
three  times  as  heavy  as  an  atom  of  hydrogen,  so 
that  caustic  soda  (NaOH)  weighs  40  (23  + 16-f  1). 
This  means  that  if  23  grams,  ounces,  or  lbs.  of 
sodium  were  cut  up  into  small  pieces  and  dropped 
into  18  grams,  ounces,  or  lbs.  of  water,  40  grams, 
ounces,  or  lbs.  of  caustic  soda  would  be  obtained, 
than  which  nothing  could  be  simpler.  All  chemical 
formulae  can  be  expressed  in  actual  weights  in  just 
the  same  manner. 

The  formulae  that  appear  so  alarming  are  merely 
this  convenient  and  scientific  kind  of  shorthand, 
the  key  to  which  will  be  found  on  page  138. 


HYDROCHLORIC  ACID. 


19 


Chlorine  is  a yellowish-green,  very  irritating  gas. 
If  the  reader  wishes  to  become  acquainted  with  it 
let  him  warm  ten  drops  of  hydrochloric  acid  with 
five  drops  of  nitric  acid  in  a test-tube  or  other  glass 
vessel,  when  fumes  of  chlorine  will  be  freely  given 
off.  This  yellowish-green  gas  combines  violently 
with  hydrogen  to  form  hydrochloric  acid  (HCl),  one 
atom  of  the  one  combining  with  one  atom  of  the 
other.  What  is  ordinarily  called  hydrochloric  acid 
and  purchased  of  a chemical  dealer  is  a solution  of 
hydrochloric  acid  gas ; this  solution  will  be  found 
to  turn  blue  litmus  red,  to  be  intensely  acid  to  the 
taste  (dilute),  and  to  be  exactly  the  opposite  of  the 
alkaline  caustic  soda. 

If  caustic  soda  be  mixed  with  hydrochloric  acid 
in  proper  proportions  a neutral  liquid  will  be 
obtained.  A good  deal  of  heat  is  given  out,  and  the 
experiment  must  be  tried  with  dilute  acid  and 
alkali.  The  resulting  liquid  is  called  “ neutral,” 
because  it  is  neither  acid  nor  alkaline,  and  has  no 
effect  on  litmus-paper ; it  is,  in  fact,  a solution  of  a 
salt — common  salt  or  sodium  chloride. 

What  has  just  happened  is  represented  in  chemi- 
cal shorthand  thus: — 

Hydrochloric  Sodium 

Acid.  Caustic  Soda.  Chloride.  Water. 

HCl  + NaOH  = NaCl  -f-  HOH. 

added  to  forms  and 

This  is  called  an  “ equation,”  because  there  is  an 
equal  quantity  of  material  on  both  sides,  but  it  is 


20 


EQUATIONS. 


arranged  differently.  Whenever  anything  happens 
in  chemistry  there  is  the  same  quantity  of  material 
at  the  end  as  there  was  at  the  beginning.  Nothing 
is  ever  destroyed;  the  different  parts  are  merely 
rearranged. 

Now  take  a solution  of  silver  nitrate.  If  you 
have  the  means  of  weighing  and  measuring  accur- 
ately, make  up  a 1 per  cent,  solution  of  silver 
nitrate  by  dissolving  1 gram  in  100  c.c.  of  distilled 
water;  fill  a burette  with  the  solution  and  run 
exactly  34  c.c.  into  a dish  or  gallipot  of  some  kind. 
Make  up  a 1 per  cent,  solution  of  sodium  chloride 
(1  gram  in  100  c.c.);  put  this  in  another  burette, 
and  out  of  this  run  10  c.c.  into  the  gallipot  con- 
taining the  34  c.c.  of  silver  nitrate.  A white 
“ precipitate  ” will  form ; shake  the  vessel  round 
and  allow  the  precipitate  a few  moments  to  settle 
to  the  bottom.  Then  add  a few  more  drops  from 
the  sodium  chloride  burette.  A fresh  white  pre- 
cipitate will  form  and  sink  to  the  bottom.  This 
precipitate  will  go  on  forming  until  11*7  c.c.  alto- 
gether of  sodium  chloride  solution  have  been  added. 
If  the  solution  be  now  allowed  to  stand  until  the 
precipitate  has  settled,  no  more  precipitate  will  form 
when  more  sodium  chloride  is  run  in.  If  the 
reader  has  not  conveniences  for  measuring,  he  must 
take  a small  quantity  of  silver  nitrate  solution  and 
add  solution  of  common  salt  in  small  quantities  at 
a time  until  no  more  precipitate  is  thrown  down. 

To  explain  what  has  been  happening,  it  is  necessary 


SILVEK  CHLORIDE. 


21 


to  say  a few  words  about  silver  nitrate.  Nitric 
acid  contains  one  atom  each  of  hydrogen  and  nitrogen 
and  three  atoms  of  oxygen.  As  hydrochloric  acid 
is  HCl,  so  nitric  acid  is  HNO3.  When  silver  (Ag) 
is  dissolved  in  nitric  acid,  the  silver  takes  the  place 
of  the  hydrogen,  producing  silver  nitrate  (AgN03). 

When  the  sodium  chloride  was  run  into  the 
silver  nitrate  in  the  experiment,  the  sodium  and  the 
silver  changed  places. 

Silver  Mtrate.  Sodium  Chloride.  Silver  Chloride.  Sodium  Nitrate. 

AgNOg  + NaCl  = AgCl  + NaNOg. 

The  white  precipitate  was  silver  chloride,  and  the 
sodium  nitrate  remained  dissolved  in  the  solution. 
Further,  it  was  seen  from  the  experiment  that  11’7 
parts  of  sodium  chloride  were  just  sufficient  to  cause 
all  the  silver  in  34*0  parts  of  silver  nitrate  to  pre- 
cipitate as  chloride.  If  the  different  parts  of  the 
equation  are  calculated  out,  it  will  be  seen  that  this 
is  the  case. 

Ag  N O3  + Na  Cl  = Ag  Cl  + Na  N O3 

108  + 14  + 48  23  + 35-5  108  + 35-5  23  + 14  + 48 

170  58-5  14^5  S 

So  that  170  AgNOg  requires  58‘5  NaCl,  or  340 
requires  117.  From  this  equation  it  will  be  seen 
also  that  from  170  parts  of  silver  nitrate  143’5 
parts  of  silver  chloride  can  be  obtained.  This 
calculation,  or  similar  calculations  with  bromide  and 
iodide  instead  of  chloride,  are  being  gone  through 


22  CHLORIDE,  BROMIDE,  AND  IODIDE. 

constantly  when  making  emulsions.  Although 
tables  are  given  to  save  time,  every  photographer 
should  know  how  to  work  out  the  figures  himself  if 
necessary. 

Potassium  (K)  is  a very  similar  metal  to  sodium, 
and  it  is  sometimes  more  convenient  to  use  potassium 
salts,  such  as  potassium  bromide  and  potassium  iodide, 
instead  of  sodium  salts,  but  the  calculations  are 
exactly  similar,  using  K (39)  in  place  of  Na  (23). 

Bromine  is  a red  liquid  and  iodine  a brownish, 
rather  metallic  looking,  solid.  They  resemble 
chlorine  very  closely,  and  silver  bromide  and  iodide 
are  very  like  silver  chloride.  Take  two  gallipots 
and  place  silver  nitrate  solution  in  each.  Into  one 
run  a solution  of  potassium  bromide,  and  into  the 
other  a solution  of  potassium  iodide.  A precipitate 
will  be  formed  in  each  case ; that  with  the  bromide 
being  yellowish- white  (silver  bromide),  and  that 
with  the  iodide  being  pale  yellow  (silver  iodide). 
These  experiments  can  all  be  performed  in  test-tubes, 
i.e.,  thin  glass  tubes  closed  at  one  end,  or  in  beaker 
flasks ; the  latter  (fig.  3)  are  useful  for  many 
purposes  in  the  work-room. 

As  silver  chloride,  bromide,  and  iodide  resemble 
one  another  so  closely  in  their  chemical  properties, 
they  can  often  be  substituted  for  one  another  partly 
or  wholly  without  introducing  any  very  great  change 
in  the  result.  In  making  emulsions  for  dry  plates 
or  in  preparing  collodion  for  wet  plates,  these  salts 
are  introduced  in  varying  proportions  to  suit  the 


EQUIVALENT  QUANTITIES. 


23 


subject.  Accordingly  it  is  important  to  know  what 
quantity  of  chloride  is  equivalent  to  a certain 
quantity  of  bromide  or  iodide,  and  vice  versa.  This 
can  be  learned  from  chemical  shorthand  at  once. 
The  formulae  for  the  three  compounds  are  AgCl, 
AgBr,  and  Agl.  An  atom  of  bromine  (Br)  weighs 
80  and  iodine  (I)  weighs  126*5 ; so  that 

Silver  chloride,  AgCl,  weighs  108+  35*5  or  143*5 

„ bromide,  AgBr,  „ 108+  80  „ 188 

„ iodide,  Agl,  „ 108  + 126*5  ,,  234*5 

From  this  it  is  clear  that  143*5  parts  of  the 
chloride  are  capable  of  doing  the  same  work  as  188 
parts  of  bromide  or  235  of  iodide.  The  following 
table  gives  equivalent  quantities  of  these  salts  to 
save  calculations. 


TABLE  III. — Equivalent  Quantities  of  Silver  Salts. 


Silver 

(Metallic). 

Nitrate. 

Chloride. 

Bromide. 

Iodide. 

1 

1*574 

1*328 

1-741 

2-176 

0-6353 

1 

0-844 

1-106 

1-38-2 

0*7523 

1*184 

1 

1-310 

1-638 

0-5744 

0-904 

0-763 

1 

1-250 

0*4595 

0-723 

0-610 

0-800 

1 

Take  the  three  vessels  containing  the  precipitates 
— silver  chloride,  bromide,  and  iodide — and  decant 
off  the  liquid  with  the  help  of  a glass  rod  as  shown 
in  the  sketch  (fig.  4).  To  the  first  add  a few  drops 


24 


EXPERIMENTS. 


of  ammonia  solution ; the  silver  chloride  will  dis- 
solve completely.  To  this  solution  add  a few  drops 
of  acid  to  neutralise  the  ammonia ; the  white  silver 
bromide  will  reappear,  showing  that,  although  it  is 
soluble  in  ammonia,  it  is  insoluble  in  acids.  To 
the  bromide  precipitate  add  a solution  of  what  is 
generally  known  as  hyposulphite  of  soda ; the  pre- 
cipitate will  dissolve  completely.  The  other  pre- 


cipitate may  be  treated  with  potassium  cyanide,  with 
a like  result. 

Now  to  go  back  to  the  first  experiment,  when 
metallic  sodium  was  added  to  water,  so  that  an 
atom  of  sodium  took  the  place  of  an  atom  of  hydro- 
gen, forming  NaOH  instead  of  HOH.  If  the  ex- 
cess of  water  be  driven  off  by  heating  the  solution, 
or  if  enough  sodium  be  added  to  combine  with  all 
the  water,  a solid  mass  of  sodium  hydrate  (caustic 
soda,  NaOH)  will  be  formed.  If  more  sodium  be 
added  to  this  and  the  mixture  be  warmed,  the  other 


OXIDES. 


25 


hydrogen  atom  will  be  turned  out  by  the  sodium, 
thus 

HOH,  then  NaOH,  then  NaONa. 

This  substance,  NugO,  is  called  “ oxide  ” of  sodium, 
and  much  resembles  the  hydrate  or  caustic  soda  in 
appearance. 

Now  add  some  caustic  soda  solution  to  a little 
silver  nitrate  solution — by  a “ little is  meant  from 
half  an  inch  to  an  inch  of  liquid  in  a small  test-tube 
or  measuring  glass.  A light  brown  precipitate  will 
sink  to  the  bottom.  This  light  brown  substance  is 
oxide  of  silver,  or  Ag20,  and  is  put  together  in  exactly 
the  same  way  as  oxide  of  sodium. 

H.O.H  H.O.H 

Na.O.Na  Ag.O.Ag 

Oxide  of  Sodium,  Oxide  of  Silver. 

The  silver  compounds  must  be  left  for  a little  while 
and  something  must  be  said  about  the  salts  of  iron, 
which  are  not  quite  so  simple  as  those  of  silver. 
Tirst  dissolve  up  a few  of  the  green  crystals  of  sul- 
phate of  iron  or  ferrous  sulphate,  as  it  is  more  cor- 
rectly called.  To  some  of  this  add  a little  caustic 
soda  and  watch  what  happens : a precipitate  is 
formed,  first  white,  then  green,  and  ultimately  brown. 
If  this  white  precipitate  could  be  kept  from  changing 
whilst  it  was  dried  and  heated,  you  would  get  an 
oxide  of  iron — “ an  oxide  ” because  there  are  more 
than  one.  This  oxide  would  be  FeO,  one  atom 
of  iron  (Fe)  being  capable  of  turning  out  both  atoms 


26 


FERROUS  AND  FERRIC. 


of  hydrogen  from  water,  or  replacing  two  atoms  of 
silver,  or  two  atoms  of  sodium,  etc.  The  white  pre- 
cipitate was  ferrous  hydrate.  As  iron  is  capable  of 
taking  the  place  of  two  atoms  of  sodium,  you  have 


so  that  ferrous  hydrate  is  Fe(OH)2. 

When  this  hydrate  is  dried  and  heated,  a particle 
or  molecule  of  water  splits  off,  leaving  the  oxide, 
FeO,  thus: — 


In  actual  practice,  however,  you  have  seen  that 
the  white  precipitate  turned  green  and  then  brown. 
The  ferrous  hydrate  was  using  the  oxygen  of  the 
air  to  convert  itself  into  another  hydrate  containing 
more  OH,  viz.,  Fe(OH)g.  From  this  you  see  that 
iron  can  combine  with  either  two  or  three  OH’s,  i.e.^ 
can  take  the  place  of  either  two  or  three  atoms  of 
hydrogen  or  silver  or  sodium,  etc.  Consequently, 
ferrous  .iron  is  always  hungry  until  it  has  got  hold 
of  the  third  OH,  or  whatever  it  may  be.  It  is  im- 
portant that  you  should  understand  this  thoroughly, 
as  it  is  the  basis  of  the  development  of  negatives. 
In  the  solution,  after  the  addition  of  the  caustic  soda 
to  the  ferrous  sulphate,  you  had  essentially  (neglecting 
the  sodium  and  the  sulphate)  water,  oxygen  from  the 


Fej 


NaOH 

NaOH 


OXIDIZING  AND  REDUCING. 


27 


air  dissolved  in  the  water,  and  a substance — ferrous 
hydrate — ready  to  pick  up  any  OH  that  might  be 
available.  The  oxygen  is  anxious  to  combine  with 
hydrogen  to  form  water,  so  that  you  have  ferrous 
hydrate  and  oxygen  with  a particle  of  water  between, 
like  a duck  and  a hen  over  a worm.  The  water 
comes  in  half,  as  the  metaphorical  worm  would  do, 
the  iron  gets  its  OH  (hydroxyl)  and  the  oxygen 
gets  its  hydrogen,  and  everybody  is  satisfied, 
thus : — 


Fe(OH)2 

HO 

Fe(OH), 

HO 

Any  substance  that  is  anxious  to  get  hold  of  hydro- 
gen acts  like  oxygen  in  presence  of  water,  or,  to  put 
it  in  different  words,  is  an  oxidizing  agent.  Chlorine 
and  bromine,  for  example,  behave  in  this  manner. 
If  you  had  added  chlorine  or  bromine  to  the  ferrous 
hydrate,  it  would  have  gone  brown  at  once.  The 
action  would  have  been  complicated,  however,  by  the 
hydrochloric  acid  formed  (see  page  19)  dissolving 
the  hydrate  to  make  ferric  chloride,  in  the  same 
way  that  sodium  hydrate  with  hydrochloric  acid 
produced  sodium  chloride. 

How  see  what  happens  when  ferrous  sulphate  is 
added  to  a silver  salt,  say  silver  nitrate : a black 
precipitate  is  formed.  The  iron,  as  it  were,  says  to 
the  silver,  “ You’ve  got  my  HO3 ; drop  it ! ” And  the 
silver  has  to  drop  it  and  become  “ reduced  ” to 


28 


COMBINING  PKOPORTIONS. 


metallic  silver,  whilst  the  ferrous  iron  appropriates 
the  NO3  to  raise  itself  to  the  ferric  state. 

It  is  quite  clear,  then,  that  an  oxidizing  agent  is 
a substance  that  is  anxious  to  take  up  hydrogen,  and, 
vice  versd,  a reducing  agent  is  a substance  that  is 
hungering  after  oxygen.  Hydrogen  itself  is  a very 
powerful  reducing  agent.  With  metallic  salts, 
oxidation  raises  them  further  from  the  metallic 
state  ; reduction  robs  them  of  whatever  other  sub- 
stance, such  as  chlorine  or  nitric  acid  (nitrate),  they 
are  combined  with,  and  brings  them  back  wholly 
or  partly  to  the  simple  metallic  condition. 

From  the  talk  about  ferrous  and  ferric  salts,  you 
have  seen  that  chemical  elements  may  combine  in 
other  proportions  than  one  to  one.  Silver  chloride 
contains  one  of  silver  to  one  of  chlorine ; ferrous  iron 
takes  two  of  chlorine  ; ferric  iron,  three  of  chlorine  ; 
in  platinic  chloride  there  is  one  of  platinum  to  four 
of  chlorine,  and  there  are  other  compounds  with  a 
higher  proportion  of  chlorine  still.  For  convenience 
in  chemical  shorthand,  the  number  of  atoms  of 
hydrogen  an  element  is  capable  of  replacing  is  de- 
noted by  dashes,  thus  : — 

Ag'Cr,  Silver  chloride. 

Fe"Cl2,  Ferrous  „ 

Fe"'Cl3,  Ferric  „ 

Pt^''Cl4,  Platinic  ,, 

Sulphuric  acid  has  the  composition  represented  in 
chemical  shorthand  as  H2SO4,  so  that,  as  ferrous 
iron  can  replace  two  H’s,  the  composition  of  ferrous 


WATER  OF  CRYSTALLIZATION. 


29 


sulphate  is  reS04.  The  green  crystals  that  you 
buy,  or  that  would  be  obtained  if  you  evaporated  a 
solution  of  ferrous  sulphate  to  a thick  syrup  and 
allowed  it  to  crystallize,  contain  water,  as  do  most 
crystals.  In  assuming  the  solid  condition  many 
substances  crystallize  in  two  or  three  different  forms 
according  to  the  amount  of  water  their  particles 
entangle.  Ferrous  sulphate  carries  down  with  it 
seven  molecules  of  water,  so  that  the  formula  for  the 
green  crystals  is  FeS04,7H20.  This  is  important, 
as  in  making  up  percentage  or  other  solutions  this 
water  has  to  be  taken  into  account.  For  instance, 
suppose  a ten  per  cent,  solution  of  ferrous  sulphate 
is  required.  Then 

FeS04(56  + 32  + 64)=152 
7H2O  (2  + 16)  =126 

278 

So  that  278  parts  of  the  crystals  only  contain 
152  parts  of  ferrous  sulphate.  To  calculate  how 
much  FeS04  must  actually  be  used,  you  make  the 
proportion  sum, 

is  to  as  is  to  the  amount  required. 

152  : 278  : : 10  : 

278  X 10  + 152  = 18*3  parts  as  nearly  as  possible. 

multiplied  divided  gives 
by  by 

A few  words  now  about  acids  ! Several  different 
acids  have  been  mentioned,  but  they  possess  one 
feature  in  common ; they  all  contain  hydrogen. 
Acids  are  salts  of  hydrogen.  Hydrochloric  acid 


30 


ACIDS. 


(HCl)  is  hydrogen  chloride  just  as  AgCl  is  silver 
chloride ; sulphuric  acid  being  hydrogen  sulphate. 
The  last  named  acid  contains  two  atoms  of  hydrogen, 
both  of  which  can  be  replaced  by  a metal,  and  there 
are  other  acids,  such  as  phosphoric  acid  (H3PO4), 
which  contain  more  than  two  atoms  of  hydrogen. 
In  the  carbon  or  organic  acids,  such  as  citric  or 
acetic  acids,  there  are  atoms  of  hydrogen  that  are 
not  replaceable,  and  their  formulae  are  liable  to 
confuse  the  reader,  but  in  the  last  chapter  (which 
see)  the  hydrogens  that  can  be  displaced  by  iron  or 
sodium  or  silver,  etc.,  to  form  salts,  are  shown  quite 
clearly. 

With  hydrochloric  acid,  where  there  is  only  one 
hydrogen,  the  latter  must  be  displaced  entirely,  but 
with  sulphuric  acid,  where  there  are  two  hydrogens, 
you  may  have  either  one  or  both  atoms  replaced  by 
a metal.  Tor  instance,  there  are  two  sodium  sul- 
phates, thus : — 

H2SO4,  Sulphuric  Acid. 

NaHSO^,  Acid  Sodium  Sulphate. 

NagSO^,  Neutral  or  normal  Sodium  Sulphate. 

The  salt  in  which  only  one  of  the  hydrogens  has 
been  displaced  has  an  acid  character,  as  you  would 
expect,  and  is  called  “ acid  sodium  sulphate.”  You 
will  understand  from  this  that  an  “ acid  ” salt 
means  a salt  in  which  the  hydrogen  is  only  partly 
displaced  by  metal.  The  term  “ bi  ” is  used  fre- 
quently instead  of  “ acid,”  so  that  NaHS04  is  gener- 
ally called  sodium  bi-sulphate. 


SULPHATE  AND  SULPHITE. 


31 


In  salts  that  are  derived  from  acids  containing 
oxygen  there  is  a possibility  of  reducing  that  oxy- 
gen. Sulphuric  acid  or  a sulphate,  for  example, 
may  be  deprived  of  one  or  two  atoms  of  oxygen, 
producing 

H2SO4,  Sulphuric  acid. 

HgSOg,  Sulphurous  acid. 

H2SO2,  Hyposulphurous  acid. 

Their  sodium  salts  are 

hTa2SO^,  Sodium  sulphate. 

Na2S03,  ,,  sulphite. 

NaoS02,  „ hyposulphite. 

This  last  salt  is  true  sodium  hyposulphite  ; the 
photographer’s  “ hypo  ” is  not  hyposulphite  of 
sodium,  correctly  speaking,  but  sodium  thiosulphate, 

^^”a2S203. 

From  all  this  the  reader  will  gather  some  idea  of 
the  way  in  which  chemical  compounds  are  named. 
The  termination  “-ide  ” signifies  a salt  consisting  of 
a metal  united  with  another  element,  such  as  silver- 
chloride  ; “-ate  ” signifies  a salt  containing  oxygen 
as  well ; “-ite  ” contains  less  oxygen  than  “-ate.” 

If  “ hypo  ” is  put  in  front  of  the  word,  it  means 
that  the  salt  is  below  the  “ -ite  ” stage.  The  prefix 
“ per  ” or  “ hyper  ” means  above,  so  that  a per- 
sulphate of  sodium  is  richer  in  oxygen  than  sulphate 
of  sodium. 

Ha\fing  said  so  much  about  acids,  it  is  necessary 
to  devote  a paragraph  to  alkalies.  You  have  seen 
at  the  beginning  of  the  chapter  that  caustic  soda  or 


32 


ALKALIES. 


sodium  hydrate  is  water  in  which  one  atom  of 
hydrogen  has  been  replaced  by  one  of  sodium. 
Caustic  potash,  or  potassium  hydrate,  is  exactly 
similar,  potassium  (K)  taking  the  place  of  sodium. 
Caustic  potash  and  caustic  soda  dissolved  in  water 
possess  a peculiar  “ alkaline  ” taste,  turn  litmus 
paper  blue,  and  neutralize  acids  to  form  salts.  An 
alkali,  therefore,  is  a soluble  hydrate.  Nearly  all 
hydrates  and  oxides,  although  not  soluble  in  water, 
have  an  alkaline  tendency,  and  possess  some  of  the 
properties  enumerated  above. 

Ammonia,  properly  speaking,  is  a gas,  not  a 
liquid.  It  is  formed  of  one  atom  of  the  element 
nitrogen,  which  constitutes  four-fifths  of  the  atmos- 
phere, combined  with  three  atoms  of  hydrogen. 
This  NH3  dissolves  in  water  with  avidity,  forming 
NH3H2O  or  NH4OH.  Eather  curiously  this  is  a 
powerful  alkali,  and  closely  resembles  caustic  potash 
or  soda  in  its  action.  So  much  is  this  so  that  NH4 
is  called  by  one  word,  “ ammonium,”  and  NH4OH  is 
ammonium  hydrate.  The  liquid  ammonia  of  the 
druggist  then  is  a strong  solution  of  ammonium 
hydrate.  This  “ ammonium  ” forms  salts  exactly 
like  sodium  or  potassium,  producing  ammonium 
chloride,  NH4CI,  ammonium  sulphate  (NH4)2S04, 
etc. 

As  caustic  potash,  soda,  and  ammonia  are  such 
strong  alkalies,  when  they  unite  with  a weak  acid 
their  salts  are  alkaline.  Carbonic  acid  is  a weak 
acid  and  sodium  carbonate  is  strongly  alkaline. 


CARBONATES. 


33 


The  bicarbonate,  although  it  is  theoretically  an  acid 
salt,  is  faintly  alkaline.  Carbonic  acid,  by  the  way, 
is  formed  whenever  carbon  (coke  or  charcoal)  or  any 
substance  containing  carbon  is  burnt  in  the  air. 
Carbon  (C)  unites  with  two  oxygens  to  make  COo, 
and  when  this  gas  dissolves  in  water  carbonic  acid  is 
formed.  The  term  “ carbonic  acid  ” is  from 
long  usage  generally  applied  to  the  CO2  gas,  but 
all  the  carbonates  are  formed  from  CO2  dissolved  in 
water,  thus, 

H20,C02  or  H2CO3,  Carbonic  acid. 

NaHCOg,  Sodium  bicarbonate. 

Na2C03,  „ carbonate. 

Sodium  carbonate  is  the  compound  used  as  an 
alkali  in  photography.  It  can  be  obtained  perfectly 
dry,  but  the  most  convenient  form  is  washing 
soda.  The  crystals  of  this  material  contain  water 
in  the  same  way  that  ferrous  sulphate  crystals 
contain  water,  the  formula  for  washing  soda  being 
Na2CO3,10H2O.  How  HagCOg  adds  up  to  106 
(46  + 12  + 48)  and  10  of  water  make  180;  so  that, 
adding  the  two  together,  286  of  washing  soda  are 
equivalent  to  180  of  dry  sodium  carbonate,  and  this 
fact  must  be  borne  in  mind  when  making  up 
solutions. 

This  is  a convenient  place  to  say  a few  words 
about  electro-chemistry.  When  two  metals,  such 
as  zinc  and  copper,  are  joined  together  and  placed 
in  a liquid  that  conducts  electricity,  such  as  dilute 

c 


34 


ELECTRO-CHEMISTRY. 


sulphuric  acid,  an  electrical  current  is  produced  and 
flows  from  the  copper  or  positive  metal  through 
the  wire,  or  whatever  it  is  that  joins  them,  to  the 
zinc  or  negative  metal,  then  through  the  acid  back 
to  the  copper  again,  completing  the  circuit.  This 
arrangement  is  called  an  electric  battery ; various 
other  combinations  of  metals  are  used  in  different 
batteries,  but  the  principle  is  the  same.  It  is  not 
necessary  to  use  two  metals  to  produce  an  electric 
current,  a metal  and  a solution  of  a metallic  salt, 
or  even  two  solutions  separated  by  a porous  parti- 
tion, being  sufficient  to  cause  a current.  It  is 
evident  that  nearly  every  chemical  change  must 
produce  an  electric  current  or  vice  versd,  and  it  is 
difficult,  if  not  impossible,  to  separate  one  from  the 
other. 

Now  try  this  experiment : Make  a little  electric 
battery  of  a strip  of  zinc  and  a strip  of  some  other 
metal,  dipping  in  dilute  acid  in  a jam-pot  or  some- 
thing of  the  kind ; connect  the  copper  strip  by  a 
wire  to  another  smaller  strip  of  copper,  and  the 
zinc  in  a similar  way  to  another  little  strip  of  zinc  ; 
allow  the  two  latter  strips  to  dip  into  a solution 
of  sulphate  of  copper  in  a beaker  or  glass  of  some 
kind,  so  that  you  can  see  what  is  going  on.  In  a 
few  minutes,  the  zinc  strip  will  have  become  coated 
with  copper,  and  if  you  had  weighed  the  copper 
strip  before  the  experiment  you  would  find  that 
some  of  it  had  dissolved.  This  is  the  principle  of 
electro-typing,  electro-plating,  electro-gilding,  and 


ELECTRO-DEPOSITION. 


35 


so  on.  If  you  had  had  a convenient  solution  of 
silver  instead  of  the  sulphate  of  copper,  silver  would 
have  been  deposited  on  the  zinc. 

As  you  will  see  in  the  next  chapter,  much  of 
what  goes  on  during  development  resembles  electro- 
plating. In  the  solution  a kind  of  “ ladies’-chain  ” 
is  taking  place,  the  atoms  of  metal  travelling  in  the 
direction  of  the  current,  to  be  deposited  finally  on 
the  negative  electrode  or  terminal  of  the  wire  con- 
nected with  the  zinc  of  the  battery  or  what  corre- 
sponds to  it.  In  developing,  it  is  very  possible  that 
each  particle  of  reduced  silver  in  the  latent  image 
acts  as  the  terminal  of  a tiny  electric  battery  or 
couple  ” as  it  is  called,  and  the  silver  from  the  sur- 
rounding silver  salts  is  deposited  on  it  to  build  up 
the  visible  image. 


36 


PHOTO-SALTS. 


CHAPTEE  III. 

The  Chemistry  of  the  Photographic  Image. 

The  chemistry  of  the  different  processes  for  pro- 
ducing and  developing  a latent  image  are  so  inter- 
woven that  it  is  convenient  to  talk  about  them  to- 
gether ; the  composition  of  the  different  plates  and 
developing  materials  will  be  considered  separately 
afterwards.  First  of  all,  however,  it  will  be 
necessary  to  say  a few  words  about  the  photo- 
chlorides and  kindred  salts  of  silver. 

The  photo-chlorides  of  silver,  which  Carey  Lea 
did  so  much  to  investigate,  are  the  compounds  pro- 
duced by  the  action  of  light  or  reducing  agents,  such 
as  ferrous  sulphate,  on  silver  chloride.  They  con- 
tain less  chlorine  than  silver  chloride,  and  may  be 
regarded  as  stepping-stones  between  silver  chloride 
and  metallic  silver.  There  seems  to  be  a consider- 
able number  of  them,  and  they  vary  in  colour  from 
white,  through  flesh-colour,  pink,  rose,  copper-red, 
reddish-purple  and  chocolate,  to  black.  They  appear 
to  be  permanent  if  kept  in  the  dark,  but  change 
rapidly  in  the  light.  More  about  these  interesting 


THERMOGRAPHIC  IMAGES. 


37 


compounds  and  about  some  curious  and  beautiful 
forms  of  metallic  silver,  which  are  soluble  in  water, 
will  be  found  in  chapter  VII. 

The  photo-bromides  and  photo-iodides  resemble 
the  photo-chlorides  very  closely.  In  all  cases  the 
presence  of  soluble  chlorides,  bromides  or  iodides, 
such  as  sodium  chloride  or  potassium  bromide,  etc., 
in  solution  hinders  the  formation  of  the  photo-salts, 
an  acid  having  the  same  effect,  whilst  an  alkali  or 
reduced  silver  hastens  their  formation. 

To  pick  up  the  thread  where  it  was  dropped  at 
the  end  of  the  last  chapter.  Hunt  found,  in  the  early 
days  of  photography,  that  invisible  images  could  be 
produced  by  heat,  and  that  these  could  be  developed 
subsequently.  If  a hot  coin  be  held  close  to  a piece 
of  clean  glass,  the  image  of  the  coin  can  often  be 
reproduced  by  breathing  on  the  glass.  The  action 
is  probably  electrical,  but  in  any  case  there  is  a 
selective  action,  so  that  the  moisture  sticks  to  one 
part  and  not  to  another.  Hunt  used  polished  metal 
and  developed  his  images  with  mercury  vapour,  the 
principle  being  the,  same. 

In  Daguerre’s  process  a polished  silver  plate  was 
exposed  to  iodine  vapour,  so  as  to  form  a thin  film 
of  silver  iodide  on  the  surface.  This  plate  was  then 
exposed  in  the  camera,  and  developed  with  mercury 
vapour.  In  this  case  the  result  was  very  different 
from  the  heat  or  “ thermographic  ” images.  The 
light  in  the  bright  parts  of  the  image  thrown  by 
the  lens  had  reduced  the  silver  iodide  in  the  thin 


38 


DAGUEEKEOTYPK 


film  on  the  surface,  and  the  liberated  iodine  probably 
acted  on  the  metallic  silver  just  behind  to  form 
more  photo-iodide,  thus  intensifying  the  effect  of  the 
light.  The  mercury  vapour  combined  chemically 
with  the  reduced  parts  of  the  plate,  so  that  a visible 
image  was  formed.  This  was  fixed  and  toned  with 
gold  salts. 

So  far  you  have  seen,  first,  a mechanical  effect 
caused  by  beat,  and  developed  mechanically;  secondly, 
mechanical  effect,  caused  by  light,  ending  in  chemical 
action,  and  extended  or  developed  by  chemical  action. 
In  the  former  case  the  invisible  or  latent  image  was 
due  probably  to  different  electrical  conditions  on 
different  parts  of  the  surface.  In  the  latter  case, 
you  have  every  reason  to  suppose  that  the  latent 
image  was  composed  of  reduced  silver  iodide  or 
photo-iodide.  I should  like  to  take  the  opportunity 
here  of  impressing  on  the  reader’s  mind  the  fact 
that  photographic  action  is  not  yet  thoroughly 
understood.  Even  in  such  a comparatively  simple 
affair  as  a Daguerreotype  plate,  the  latent  image 
cannot  be  taken  out  and  examined.  In  wet  plates, 
and  more  especially  dry  plates,  the  conditions  are 
much  more  complicated,  so  that  the  difficulty  in 
finding  out  what  happens  is  greatly  increased. 
Consequently,  scientific  guesswork  has  to  be  brought 
to  the  aid  of  the  investigator ; the  guesswork  is  of 
a very  shrewd  order,  but  it  is  guesswork  none  the 
less.  When  you  consider  that  in  a wet  plate,  for 
example,  you  have  an  almost  microscopically  thin, 


THE  LATENT  IMAGE. 


39 


and  by  no  means  simple,  film  to  start  with,  and  that 
only  the  outermost  particles  of  this  thin  film  appear 
to  be  affected  directly  by  the  light,  you  will  see 
that  it  is  not  easy  to  lay  down  the  law  as  to  what 
happens  in  the  film. 

A wet  plate  after  exposure  consists  essentially  of 
a film  of  collodion  containing  silver  iodide,  a part  of 
which  has  been  acted  upon  by  the  light,  and  this  is 
covered  with  a layer  of  silver  nitrate.  The  developer, 
made  up  of  a solution  of  ferrous  sulphate  containing 
a little  acid — generally  acetic  acid — is  poured  over 
this.  Ferrous  sulphate  alone  would  reduce  the 
silver  nitrate  at  once,  covering  the  plate  with  a black 
deposit  of  metallic  silver ; but  the  presence  of  the 
acid  hinders  this  action,  so  that  the  reduction  only 
proceeds  slowly.  Probably  the  first  action  of  the 
developer  is  to  reduce  to  the  metallic  state  the 
photo-iodide  that  has  already  been  acted  upon  by 
the  light.  This  forms  a nucleus  for  the  deposit  of 
silver  from  the  reduced  nitrate,  in  a similar  manner 
to  the  selective  action  in  the  thermographic  image, 
and  this  reduced  silver  is  built  up  on  the  latent 
image  forming  the  visible  image  of  the  wet  plate. 

As  development  proceeds  the  ferrous  sulphate 
becomes  oxidized  (see  p.  27)  and  loses  its  reducing 
power,  so  that  the  formation  of  the  image  progresses 
more  and  more  slowly,  or  in  photographic  language, 
the  developer  becomes  more  and  more  restrained. 
It  is  obvious  that  if  any  substance  be  present  that 
will  absorb  the  acid  given  off  by  the  silver  on  reduc- 


40 


poitevin’s  experiment. 


tion  the  formation  of  the  image  will  go  on  more 
rapidly.  In  1866  Poitevin  tried  the  experiment  of 
squeezing  a collodion  film  containing  silver  iodide, 
free  from  excess  of  nitrate,  on  to  a silver  plate,  and 
treating  a glass  plate  in  a similar  manner.  Both 
were  exposed  to  light  and  developed.  The  film  on 
the  silver  plate  showed  a considerable  image,  being 
very  much  denser  than  that  on  the  glass  plate,  but 
the  latter  did  show  a slight  image.  Prom  this  it  is 
clear  that  an  image  of  reduced  silver  can  be  formed 
even  when  there  is  nothing  to  absorb  the  iodine  or 
whatever  it  may  be  that  is  given  off.  It  is  con- 
jectured that  in  such  a case  a compound  must  be 
produced  similar  to  KI3 — the  dark  substance 
obtained  on  dissolving  iodine  in  potassium  iodide. 
The  statement  that  an  absorbent  of  iodine,  chlorine, 
or  acids,  such  as  metallic  silver,  hastens  development, 
however,  is  amply  proved  by  this  experiment. 

In  making  a wet  plate  for  use,  collodion  (see 
chap.  XIV.)  is  iodized  by  dissolving  soluble  iodides 
or  even  iodine  itself  in  the  collodion.  Except  for 
process  work,  it  is  usual  to  employ  bromide  as  well 
as  iodide.  The  latter  alone  gives  a hard  negative, 
and  bromide  alone  a flat  detailed  negative ; the 
proportion  of  the  two  can  be  varied  to  suit  the 
subject.  The  bromides  and  iodides  of  cadmium 
and  ammonium  are  those  generally  used. 

The  glass  plates  to  be  coated  must  be  carefully 
cleaned  and  polished  with  tripoli,  whiting,  or  rouge, 
or  better,  by  soaking  in  sulphuric  acid  and  bi- 


PREP  A KING  WET  PLATES. 


41 


chromate  of  potash  (see  p.  14) ; then  edged  with 
india-ruhber  solution  and  given  a first  coat  or  sub- 
stratum of  albumin  or  gelatin  to  which  a few  drops 
of  ammonia  have  been  added.  This  preliminary 
edging  and  coating  is  to  prevent  the  collodion 
slipping  or  coming  away  from  the  glass.  The 
iodized  collodion  is  poured  on  to  the  plate  and 
distributed  evenly  by  rocking,  the  excess  being 
drained  off  at  one  corner.  In  subsequent  opera- 
tions this  corner  should  always  be  kept  at  the 
bottom.  The  plate  is  then  immersed  in  a bath 
of  silver  nitrate  which  is  generally  made  faintly  acid 
with  nitric  acid.  The  silver  nitrate  is  converted  into 
bromide  and  iodide  (see  p.  22)  and  the  plate  is  ready 
for  use.  As  this  iodide  is  soluble  in  silver  nitrate, 
the  silver  bath  is  saturated  with  iodide  before  use 
by  adding  a few  grains  of  potassium  iodide,  and 
filtering  ofi'  any  undissolved  precipitate  of  silver 
iodide. 

After  exposure  the  plate  is  developed  by  pouring 
over  it  a solution  of  ferrous  sulphate  made  acid 
with  acetic  acid.  Ammonio-ferrous  sulphate  and 
copper  sulphate  are  used  sometimes  in  the  de- 
veloper; the  former  replaces  part  of  the  ferrous 
sulphate,  acting  more  slowly,  and  the  latter  acts 
as  a restrainer. 

The  positives  on  glass,  made  by  the  wet  plate 
process,  are  really  negatives  which  receive  a less 
exposure  in  the  camera  than  is  required  for  the 
ordinary  negative,  and  are  coated  on  the  film  side 


42 


FORMULA  FOR  WET  PLATES. 


with  black  varnish  after  development.  Conse- 
quently the  black  of  the  varnish  shows  through 
the  transparent  parts  of  the  plate,  and  the  silver 
deposit  shows  white  by  reflection,  so  that  the  nega- 
tive is  turned  into  a positive. 

The  various  formulae  for  producing  a flnished 
wet  plate  negative  are  as  follows,  those  marked 
with  an  asterisk  being  employed  at  the  Bolt  Court 
Process  School : — 


The  Substratum.^ 

Sheet  gelatin,  . 2*5  grams,  . 22  grs. 

Ammonia  '880,  . . 4 c.c.,  . 40  minims. 

Water  (distilled),  . 1000  c.c.,  . 20  fl.  ozs. 

Rubber  Solution  for  Edging,"^ 

Pure  rubber  cut  into  small  pieces,  1 gram,  . 20  grs. 

Benzole,  ....  100  c.c.,  . 5 ozs. 

Silver  Bath  for  Sensitizing.^ 

Silver  nitrate,  . . 68  grams, . 600  grains. 

Water  (distilled),  . 1000  c.c.,  . 20  fl.  ozs. 

Pot.  iodide  (10%  solution),  1 c.c.,  . 60  minims. 

Sodium  carbonate  cryst.,  3'5  c.c.,  . 30  grs. 

Dissolve  the  silver  nitrate  in  one-quarter  of  the 
total  water,  then  add  the  potassium  iodide,  and 
shake ; when  the  precipitate  has  dissolved  add  the 
sodium  carbonate  dissolved  in  part  of  the  water, 
shake,  and  add  the  rest  of  the  water.  Acidify 
with  a few  drops  of  107o  nitric  acid. 


COLLODION  FORMULAE. 


43 


Collodion,'^ 

Plain  collodion,  . , 750  c.c.,  . 15  ozs. 

lodizer  (B.  solution),  . 250  c.c.,  . 5 ozs. 

1 

lodizer  {B,  Solution). 

Iodine,  . . *45  gram,  . . .2  grs. 

Alcohol  (ethyl),  100  c.c.,  . . . 1 oz. 

The  iodizer  must  be  mixed  with  the  collodion 
in  the  proportion  given,  at  least  24  hours  before 
use.  Store  in  a cool  place,  and  do  not  disturb  the 
sediment. 


Collodion  {another  Formula). 


Plain  collodion,  . 100  c.c.,  . 
Cadmium  iodide,  . *1  gram. 

Ammonium  iodide,  ‘7  ,, 

Ammonium  bromide,  *4  „ 


1 oz. 

J grain. 

3 grains. 
1 2 
^3 


The  iodides  and  bromide  may  be  dissolved  in 
the  collodion,  which  is  then  suitable  for  general 
purposes.  The  proportions  can  be  varied  to  suit 
the  subject  in  accordance  with  the  following  tables, 
remembering  that  cadmium  has  a tendency  to 
make  the  collodion  granular.  The  table  of  chlorides 
is  added  for  convenience. 


44 


BROMIDE  AND  IODIDE  EQUIVALENTS. 


TABLE  IV. — Equivalent  Quantities  of  Different 
Bromides. 


Bromine. 

Am- 

monium 

Bromide. 

Potassium 

Bromide. 

Sodium 

Bromide. 

Cadmium 

Bromide 

+4H2O. 

Zinc 

Bromide. 

Silver 

Bromide. 

1 

1-225 

1-488 

1-287 

2-150 

1-406 

2-350 

0-816 

1 

1-214 

1-055 

1-754 

1-147 

1-918 

0-672 

0-823 

1 

0-865 

1-445 

0-945 

1-579 

0-777 

0-952 

1-156 

1 

1-671 

1-092 

1-8-26 

0-465 

0-570 

0-692 

0-599 

1 

0-654 

1-092 

0-711 

0-871 

1-058 

0-915 

1-529 

1 

1-670 

0-422 

0-521 

0-633 

0-548 

0-914 

0-600 

1 

TABLE  V. — Equivalent  Quantities  of  Different 
Iodides. 


Iodine. 

Am- 

monium 

Iodide. 

Potassium 

Iodide. 

Sodium 

Iodide. 

Cadmium 

Iodide. 

Zinc 

Iodide. 

Silver 

Iodide. 

1 

1-142 

1-307 

1-181 

1-441 

1-255 

1-853 

0-876 

1 

1-145 

1-035 

1-262 

1-099 

1-624 

0-765 

0-874 

1 

0-903 

1-102 

0-960 

1-418 

0-847 

0-967 

1-107 

1 

1-220 

1-063 

1 -570 

0-694 

0-793 

0-907 

0-820 

1 

0-871 

1-286 

0-797 

0-910 

1-042 

0-941 

1-148 

1 

1-477 

0-539 

0-599 

0-706 

0-637 

0-777 

0-678 

1 

WET  PLATE  DEVELOPERS. 


45 


TABLE  VI. — Equivalent  Quantities  of  Different 
Chlorides. 


Ciiloiine 

Ammonium 

Chloride. 

Sodium 

Chloride. 

Potassium 

Chloride. 

Cadmium 

Chloride. 

Silver 

Chloride. 

1 

1-507 

1*648 

2-101 

2*575 

4*042 

0*663 

1 

1-093 

1*394 

1*710 

2-682 

0*607 

0*914 

1 

1-275 

1-564 

2-453 

0-475 

0-717 

0*784 

1 

1*226 

1*9-23 

0-388 

0-584 

0*639 

0-818 

1 

1*570 

0*247 

0*373 

0*408 

0-520 

0*630 

1 

If  the  collodion  becomes  too  thick  it  may  be 
“ thinned  ” by  adding  a little  of  a mixture  of  2 
parts  ether  (*730)  to  1 part  alchohol  (*805).  In  the 
wet  plate  process  methylated  alcohol  and  ether 
must  not  be  used  on  any  account. 

Developing  Solution  for  Negatives.'^' 

Ferrous  sulphate,  34 ‘5  grams,  . 300  grains. 

Acetic  acid  glacial,  52  c.c.,  . 500  minims. 

Eectified  spirit,  . 31  ,,  . 300  ,, 

Water  (distilled),  1000  „ . 20  ozs. 


Developing  Solution  for  Positives, 


Pyrogallic  acid,  25  grams,  . 
Acetic  acid,  . 4 c.c.. 

Alcohol,  . 5 ,, 

Water,  100  „ 


5 grains. 
100  minims. 
120  „ 

5 ozs. 


Fixing  Solutions. 

A.  Potassium  cyanide,  . 50  grams,  . 1 oz. 

Water,  . . . 1000  c.c.,  . . 20  ozs. 

Take  care  that  the  cyanide  is  fresh. 


46 


DRY  PLATES. 


B.  Sodium  thiosulphate  (hypo),  200  grams,  4 ozs. 

Water,  ....  1000  c.c.,  . 20  ozs. 

Either  A.  or  B.  may  be  used. 

For  intensification  and  reduction  see  chap.  VI.  j 
Further  information  about  the  wet  plate  process  | 
will  be  found  in  Wet  Collodion  Photography ^ byj 
Charles  W.  Gamble.  I 

The  dry  plate  differs  from  the  wet  plate  in  many 
important  respects.  Silver  bromide  and  a little! 
iodide,  or  rather  the  materials  to  produce  these—' 
silver  nitrate  and  potassium  or  ammonium  bromide 
and  iodide — are  incorporated  . in  an  emulsion  of  • 
gelatin,  which  is  spread  on  glass  plates  or  some 
other  stiff  material,  such  as  celluloid,  and  allowed 
to  dry.  Collodion  is  sometimes  employed  instead 
of  gelatin ; the  first  dry  plates  having  been  made  of 
collodion  emulsion  before  gelatin  was  thought  of. 
Before  coating  the  plates,  all  excess  of  potassium 
and  ammonium  bromides  and  iodides,  etc.,  are 
removed  from  the  emulsion  by  prolonged  soaking 
in  water,  the  sensitiveness  of  the  plate  depending 
to  a large  extent  on  the  thorough  removal  of  these 
salts. 

After  exposure  to  light  in  the  camera  quite  a 
different  state  of  things  exists  to  that  on  the  wet 
plate.  The  silver  salt  (bromide  mostly)  is  im- 
bedded in  gelatin,  and  is,  therefore,  much  less  open 
to  attack  by  the  developer,  and  there  is  no  silver 
nitrate  present.  Two  consequences  arise  from  this : 
The  silver  image  cannot  be  built  up  above  the 


ACTION  OF  THE  GELATIN. 


47 


latent  image,  as  in  the  absence  of  silver  nitrate 
there  is  no  material  to  build  from,  so  that  the 
image  must  be  formed  from  the  silver  bromide  in 
the  emulsion;  moreover,  the  silver  image  is  sunk 
downwards  into  the  film  instead  of  being  built  up 
above  the  latent  image.  Secondly,  as  no  easily 
reducible  silver  salt  is  present,  much  more  powerful 
developers  or  reducing  agents  can  be  used  than 
sulphate  of  iron  or  other  ferrous  salts. 

Although  a further  reference  will  be  made  to 
gelatin  in  the  chapter  on  developers,  in  connection 
with  pyrogallic  acid,  etc.,  a few  words  here  about 
the  complications  introduced  by  the  gelatin  will 
not  be  amiss.  In  the  first  place,  gelatin  is  a most 
complicated  body  itself,  containing  carbon,  hydro- 
gen, nitrogen,  and  oxygen,  and  its  chemical  structure 
is  not  known,  so  that  when  other  substances,  such 
as  silver  bromide,  are  mixed  with  it,  complicating 
matters  still  further,  it  is  not  easy  to  find  out 
exactly  what  happens.  Either  the  silver  bromide, 
before  exposure,  may  lie  perfectly  inert,  like  so 
much  shot  in  the  gelatin,  or  it  may  combine  bodily 
with  the  gelatin,  or  some  interchange  may  take 
place  between  them;  the  combination,  if  it  exists, 
is  probably  a loose  one.  In  any  case  the  ultimate 
effect  is  to  allow  the  silver  bromide  to  present  a 
large  surface  to  the  action  of  the  light.  The  pro- 
cess of  stewing  the  emulsion  or  mixing  ammonia 
with  it,  both  of  which  have  such  a strong  effect 
in  adding  to  the  sensitiveness  of  the  plate,  probably 


48 


THE  BUILDING  OF  THE  IMAGE. 


act  by  causing  a most  intimate  mixture  of  silver 
bromide  and  gelatin.  When  the  plate  is  exposed,  and 
still  more  when  it  is  developed,  the  gelatin  probably 
increases  the  sensitiveness  by  absorbing  the  free 
bromine  when  the  bromide  is  reduced,  in  the  same  way 
that  the  metallic  silver  acted  in  Poitevin’s  experiment. 

It  is  a doubtful  point  whether  the  silver  bromide 
that  has  not  been  touched  by  the  light,  as,  for 
example,  the  deeper  parts  of  the  film  in  an  under- 
exposed plate,  can  be  reduced  by  the  developer,  so  as 
to  help  in  building  up  the  image.  As  the  reader  prob- 
ably knows  from  bitter  experience,  the  shadows  and 
detail  in  the  half-tones  of  a badly  under-exposed 
plate  remain  absolutely  unreduced,  even  after  pro- 
longed development.  On  the  other  hand,  Abney 
tried  the  experiment  of  exposing  a gelatino-bromide 
plate  in  the  camera  and  then  covering  it  with  a 
collodio-bromide  emulsion.  On  development,  the 
two  films  were  separated,  and  it  was  found  that 
each  contained  an  image,  so  that  whilst  the  image 
was  developing  downwards  in  the  ordinary  way  in 
the  gelatino-bromide  film,  it  was  being  added  to 
from  above  by  the  silver  bromide  in  the  superposed 
film  that  had  never  seen  the  light.  This  result 
was  confirmed  by  an  experiment  of  Eder’s,  who  suc- 
ceeded in  developing  the  image  completely  through 
a very  thick  and  opaque  film.  When  something  is 
known  with  certainty  about  the  nature  of  the  latent 
image,  it  will  be  possible  perhaps  to  say  what  is  the 
correct  view. 


COLLODION  DRY  PLATES. 


49 


A collodion  dry  plate  is  made  as  follows ; — 


Alcohol  ('820), 

Ether  (-730),  . 

B.  Zinc  bromide, 

Alcohol, 

Nitric  acid, 

C.  The  same  as  B. 

D.  Silver  nitrate,  . 

Water  (warm). 

Alcohol  (warm). 

Nitric  acid. 

Add  the  alcohol  after  the 


40  grains. 

1 oz. 

2 ozs. 

3  grams,  . 40  grains. 

1 C.C.,  or  sufficient  to  dis- 

solve the  solid. 

2 drops,  . 2 drops. 

9 grams,  . 130  grains. 

7 or  8 C.C.,  ^ oz. 

20  C.C.,  . I oz. 

4  drops,  . 4 drops. 

crystals  have  dissolved, 


A,  Pyroxyline  (see  p.  128),  3 grams, 

30  C.C., 

60  C.C., 


and  mix  thoroughly. 

When  all  is  ready  put  A in  a wide-mouthed  bottle 
sufficient  to  contain  the  whole ; add  B,  and  shake 
round.  To  the  mixture  add  two-thirds  of  D,  shaking 
round  the  while  ; then  the  whole  of  C,  still  shaking 


or  stirring  ; then  the  remainder  of  D. 


The  emulsion  may  be  used  as  it  is  or  washed. 
When  the  plate,  which  must  be  edged  with  rubber  as 
described  in  the  wet  plate  process,  has  been  coated 
by  pouring  the  emulsion  in  a puddle  in  the  middle, 
and  making  it  flow  all  over  the  surface  by  tilting,  it 
is  allowed  a few  seconds  to  set  and  is  then  washed 


by  pouring  water  over  it.  This  removes  any  soluble 
salts  and  renders  the  emulsion  more  sensitive. 

Any  weak  developer  (1  grain  of  pyro.  to  the  oz. 
for  example)  may  be  used  with  these  plates,  and 
they  may  be  fixed  with  potassium  cyanide  or  sodium 

D 


50 


GELATINO-BROMIDE  EMULSION. 


thiosulphate  (hypo),  as  given  for  wet  plates,  prefer- 
ably the  former.  The  plates  should  be  under- 
developed, as  compared  with  gelatine  dry  plates,  and 
then  intensified  (see  chap.  VI.). 

There  are  numerous  formulae  for  making  gelatine 
dry  plates,  and  the  proportions  of  bromide  and 
iodide  vary  according  to  the  object  for  which  the 
plates  are  intended  to  he  used.  The  following 
formula,^  due  to  E.  Child  Bayley,  may  be  taken  as 
an  example  of  a gelatine  bromo-iodide  emulsion. 

A.  Potassium  bromide,  . 43  grams,  IJ  ozs. 

Distilled  water  up  to  . 300  c.c., . 10  „ 

B.  Silver  nitrate,  re-crystallized,  52  grams,  If  ,, 

Distilled  water  up  to  . 360  c.c.,  . 13  „ 

C.  Potassium  iodide,  . . 1*6  grams,  25  grains. 

Distilled  water  up  to  . 60  c.c.,  . 2 ozs. 

The  proportions  in  these  stock  solutions  are 
sufficient  to  make  twelve  batches  of  emulsion  of 
half-a-pint  each.  Solution  B should  be  rendered 
faintly  acid  to  litmus  paper  by  adding  two  or  three 
drops — not  more — of  acetic  or  nitric  acid. 

For  use  take 

A.  75  c.c.  (If  ozs.)  containing  10*75  grams  of 

potassium  bromide. 

B.  90  c.c.  (3f  ozs.)  containing  13  grams  of  silver 

nitrate. 

C.  15  c.c.  (5  drams)  containing  0*4  grammes  of 

potassium  iodide. 

* A full  account  of  emulsion  making,  from  which  this  formula  is 
taken,  will  be  found  in  Vol.  II.  of  The  Photograin,  p.l52.  Other 
formulae,  varied  to  suit  the  most  exacting  tastes,  will  be  found  in 
the  different  year  books  of  the  photographic  journals. 


MAKING  THE  EMULSION. 


51 


A is  placed  in  a large  (20  oz.)  flask,  B in  a 
smaller  flask.  Two  grammes  of  hard  (Heinrich’s) 
gelatine  are  weighed  out  and  allowed  to  soak  for  an 
hour  in  the  cold  bromide  solution  in  the  larger 
flask.  Both  flasks  are  brought  to  160°  F.  by  placing 
in  a saucepan  half  full  of  hot  water,  and  testing 
with  a thermometer.  The  contents  of  the  smaller 
flask  are  then  added  in  smaller  quantities  at  a time 
to  the  gelatine  and  bromide  in  the  larger  flask, 
shaking  the  while.  When  the  whole  mixture  is 
made  C is  added,  and  the  emulsion  is  placed  in  a 
covered  earthenware  jar  to  stew  in  the  saucepan  for 
an  hour  or  so.  The  jar  is  supported  by  passing 
through  a tin  plate  on  the  top  of  the  saucepan,  so 
that  the  bottom  of  the  jar  is  about  an  inch  from  the 
bottom  of  the  saucepan.  At  this  point  the  emulsion 
should  be  tested  by  placing  a drop  on  a piece  of 
clean  glass,  taking  it  out  of  the  dark  room,  where 
all  the  operations,  except  the  weighing  and  making 
up  of  the  stock  solutions  are  conducted,  and  looking 
through  it  at  a candle  flaine.  The  emulsion  should 
not  appear  gritty  or  strongly  coloured. 

After  stewing  in  water,  boiling  gently  for  an  hour 
or  so,  until  it  appears  almost  blue  on  examining  a 
drop  by  the  candle  flame,  the  emulsion  is  allowed  to 
cool,  10  grams  more  gelatin,  which  have  been  soaking 
in  cold  water  for  an  hour,  are  added,  and  the  whole 
well  stirred  until  dissolved,  when  it  is  allowed  to 
set.  The  cold  emulsion  is  washed  to  soak  out  any 
soluble  bromide,  iodide,  and  nitrates,  by  squeezing  it 


52 


COATING  THE  PLATE. 


many  times  through  net  or  canvas  under  water. 
The  emulsion  is  then  warmed  to  120°  F.,  when  the 
following  is  added,  a few  drops  at  a time,  and  the 
whole  filtered  through  calico  or  chamois  leather : — 

Chrome  alum  (1  per  cent,  solution),  10  c.c.,  3 drams. 

Alcohol,  . . . . . 40  C.C.,  IJ  ozs. 

The  plates  to  be  coated  must  be  cleaned  thor- 
oughly by  washing  with  strong  soda,  rinsing  well, 
and  allowing  to  dry.  It  does  not  pay  as  a rule  to 
re -coat  old  negative  glass.  The  coating  may  be 
performed  with  emulsion  warmed  up  again  to  105° 
F.,  in  a somewhat  similar  manner  to  that  described 
under  wet  plates.  More  material,  however,  must  be 
run  on  to  the  plate,  and  very  little  need  be  drained 
off.  The  plate  is  rocked  for  some  time,  and  then 
placed  on  a carefully  levelled  piece  of  glass  to  set. 
Drying  must  be  performed  in  a dark  room,  or  well- 
ventilated  cupboard  as  free  as  possible  from  dust. 

Kote. — Never  'pack  plates  in  newspaper  under  any 
circumstances,  as  the  print  will  be  reproduced  on 
development.  Grooved  cardboard  boxes  form  the 
best  packing. 


STANDARD  IRON  DEVELOPER. 


53 


CHAPTER  IV. 

Developers. 

By  this  time  the  reader  understands  a good  deal 
about  the  general  principles  of  development.  So 
far,  however,  acid  iron  developers  only  have  been 
talked  about.  In  a gelatin  dry  plate  there  is  no 
easily  reducible  silver  nitrate  present,  and  the  silver 
bromide  itself  is  protected  to  some  extent  by  the 
gelatin,  so  that  much  more  powerful  developers  can 
be  used  than  with  wet  plates,  and  alkalies  can  be 
introduced,  which  adds  greatly  to  the  rapidity  of 
the  plates. 

The  acid  iron  developer  is  very  suitable  for 
gelatin  plates,  giving  very  vigorous  negatives,  al- 
though it  is  necessary  for  the  exposure  to  be  cor- 
rectly made.  This  developer  is  used  in  most 
standard  work  as  it  causes  no  stain  in  the  film. 
The  following  is  the  standard  formula  used  in  speed- 
testing on  the  Hurter  and  Driffield  system,  which 
will  be  referred  to  again  directly.  The  formula, 
which  works  excellently,  is  due  to  Mr  Cadett. 
Ferrous  oxalate  is  the  iron  salt  used  as  a reducing 


54 


STANDARD  IRON  DEVELOPER. 


agent ; instead  of  the  oxalate  itself,  however,  the 
materials  for  making  the  oxalate,  namely  ferrous 
sulphate  and  potassium  oxalate,  are  employed. 

Ferrous  Potassium  Ferrous  Potassium 

Sulphate.  Oxalate.  Oxalate.  Sulphate. 

FeSO^  + K2C.2O4  = FeCgO^  + 

The  potassium  sulphate  produced  does  not  inter- 

fere with  the  development. 


Ferrous  Oxalate  Formula. 


A.  JNeutral  oxalate  of  potassium,  200  grams,  1 part. 


Distilled  water, 

B.  Sulphate  of  iron. 
Citric  acid, 
Distilled  water, 

C.  Potassium  bromide, 
Distilled  water. 


. 800  C.C.,  . 4 parts. 

. 100  grams,  1 part. 

1 gram,  „ 
300  C.C.,  . 3 parts, 
1 gram,  1 part. 

. 100  C.C.,  100  parts. 


For  test  use  take  A,  100  parts  ; B,  25  parts  ; 
C,  10  parts,  in  the  order  named.  Make  the  devel- 
oper up  to  a temperature  of  65°  F.  and  develop  for 
live  minutes ; then,  without  washing,  fix  in  a bath 
of  sodium  thiosulphate  (hypo)  made  up  of  1 part 
to  3 parts  of  water ; then  after  thorough  washing, 
place  the  plate  in  a 2°/^  solution  of  hydrochloric 
acid  to  remove  lime  or  other  stains,  and  finally  wash 
well. 

The  addition  of  a few  drops  of  1%  sodium  thio- 
sulphate (hypo)  solution  to  each  ounce  accelerates 
the  development  of  under-exposed  plates  when  using 


INFLUENCE  OF  TEMPERATURE. 


55 


a ferrous  oxalate  developer.  The  exact  action  is 
not  known. 

When  using  the  above  formula  for  ordinary 
studio  or  landscape  work,  it  is  a convenient  plan 
to  commence  development  with  an  old  developer. 
This  contains  bromide  from  the  reduction  of  the 
silver  bromide  in  the  film,  so  that  there  is  no 
occasion  to  add  bromide  when  working  with  an  old 
developer.  Many  photographers  stand  the  bottle 
containing  the  old  developer  in  the  sun  to  re- 
generate it,  the  light  reducing  the  ferric  oxalate  to 
ferrous  oxalate,  which  can  be  used  over  again. 

Ferric  oxalate.  Ferrous  oxalate.  Carbonic  acid. 

Fe2(C20^)3  + light  = 2FeC20^  + 2COo. 

In  the  directions  given  above  for  using  the  ferrous 
oxalate  developer,  the  correct  temperature  for 
development  was  stated  to  be  65°  F.  For  standard 
work,  such  as  testing  the  speed  of  plates,  it  is 
necessary  to  have  the  temperature  as  uniform  as 
possible,  and  even  in  ordinary  work,  although  ex- 
cessive accuracy  need  not  be  observed,  it  is  well 
to  always  develop  as  far  as  possible  at  the  same 
temperature.  Many  photographers  know  the  im- 
portance of  employing  a thermometer,  but  many 
others  fail  to  realize  the  marked  effect  increase  of 
temperature  produces  in  hastening  development. 
In  some  experiments  made  recently  by  the  author,  a 
difference  of  15° — from  55°  to  70°  F. — -caused  an 
increase  in  the  density  of  about  one-third.  From 


i 


56 


EESTRAINERS. 


this  it  is  clear  that  an  under-exposed  plate  should 
be  developed  with  a warm  developer  at,  say,  70°  F, 
and  an  over-exposed  plate  with  a cold  developer  at, 
say,  45°  to  55°  F. 

This  is  a convenient  stage  to  talk  about  restrainers. 
It  was  seen  (p.  37)  that  all  soluble  haloid  salts 
(chlorides,  bromides,  and  iodides)  had  a tendency  to 
hinder  the  reduction  of  the  bromide  and  kindred 
salts  of  silver.  Their  principal  action  is  to  form  a 
double  salt,  which  is  more  soluble  than  silver  bromide, 
so  that  potassium  bromide  in  the  developer  always 
dissolves  silver  bromide  out  of  the  film.  This  double 
salt  is  much  less  easily  broken  up  by  the  reducing 
agent,  so  that  the  action  is  much  slower.  As  any 
soluble  haloid  can  be  used,  common  salt  may  be  used 
as  a restrainer  in  the  absence  of  potassium  bromide. 
The  reason  why  acids  act  as  restrainers  was  ex- 
plained on  page  40.  It  is  advisable  to  always 
work  with  some  bromide  in  the  developer,  as  other- 
wise the  image  comes  up  much  too  quickly  and  the 
silver  is  apt  to  be  reduced  to  a greater  or  lesser 
extent  over  the  whole  plate,  causing  “ fog  ” and 
obscuring  the  finer  detail. 

All  the  organic  developers  in  general  use  bear 
a close  chemical  resemblance.  Phenol  (carbolic 
acid)  is  the  base  of  them  all,  and  phenol  itself  is 
benzene  in  which  one  hydroxyl  (OH)  has  taken 
the  place  of  one  atom  of  hydrogen.  Benzene,  CgHg, 
is  always  represented  in  chemistry  like  this. 


PYROCATECHIN,  RESORCIN,  HYDROQUINONE.  57 


H 

1 

H 

1 

1 

C 

(i 

H— C C— H 

H— C C— OH 

1 1 phenol  being 

1 1 

H-C  C— H 

H— C C— H 

V 

\/ 

c 

1 

C 

1 

1 

H 

1 

H 

Pyrocatechin,  resorcin,  and  hydroqninone  are  di- 
phenols, i.e.^  they  contain  two  OH’s, 


OH 

1 

OH 

1 

OH 

1 

C 

c 

c 

H— C C— OH 

1 1 

H— C C— H 

H-C  C-H 

1 1 

1 1 

H— C C— H 

1 1 

H— C C— OH 

1 1 

H_C  C— H 

V 

V 

V 

C 

1 

C 

1 

C 

1 

H 

1 

H 

H 

Pyrocatechin. 

Resorcin. 

Hydroquinone, 

1-2 

1-3 

1-4 

the  difference  being  that  the  atoms  are  arranged 
differently,  all  three  compounds  having  the  formula 

(OH),. 

Pyrogallic  acid  is 

a tri-phenol,  having  the  formula 

06113(011)3,  and  is 

still  the  most 

extensively  used 

of  all  developers. 

It  is  very  soluble  in  water, 

58 


ACTION  OF  SULPHITES. 


forming  a 40  per  cent,  solution  when  saturated.  It 
is  soluble  also  in  alcohol,  ether,  and  glycerine. 
Like  phenol  (carbolic  acid),  it  is  not  a true  acid,  such 
as  sulphuric  acid,  and  its  proper  chemical  name  is 
pyrogallol.  It  does  form  a combination  with  alkalies, 
however,  and  in  this  condition  is  a very  powerful 
reducing  agent.  If  left  exposed  to  the  air,  it 
absorbs  oxygen  rapidly,  turning  first  yellow,  then 
brown,  and  finally  black.  The  exact  nature  of  the 
oxidation  compounds  formed  are  not  accurately 
known.  These  brown  products  have  a strong  staining 
action  on  the  gelatin  so  that  under-exposed  negatives 
are  much  more  liable  to  be  stained  as,  not  only  are 
they  in  the  developer  for  a much  longer  time,  but 
the  pyrogallate  (i.e.,  the  compound  of  the  pyrogallic 
acid  with  the  alkali)  is  much  more  highly  oxidised 
through  contact  with  the  air  all  the  while.  It  has 
been  found  that  a sulphite  has  the  power  of  pre- 
venting this  staining  to  a large  extent.  Sulphite  of 
soda,  Na2S203,  is  generally  employed,  but  sometimes 
the  metabisulphite  of  potassium  (K2S2O5)  takes  its 
place.  The  drawback  to  the  last-named  is  that  it 
renders  the  solution  very  acid  after  a short  time. 
Only  one  quarter  the  amount  of  metabisulphite  is 
required,  as  compared  with  the  crystallized  sulphite. 

As  regards  the  influence  of  the  quantity  of  sul- 
phite in  the  developer  on  the  resulting  negative, 
sulphite  has  a distinct  restraining  action  on  the 
actual  deposit  of  silver,  and  if  a very  large  propor- 
tion of  sulphite  be  present  the  developer  almost 


PYRO-STAIN. 


59 


stops  working.  The  diminution  of  the  yellow  stain 
in  the  negative,  howeyer,  is  very  marked  as  the 
sulphite  is  increased.  The  reduction  in  the  quantity 
of  sulphite  from  5 to  grains  to  the  fluid  ounce  of 
developer,  in  some  recent  experiments  by  the  author 
doubled  the  yellow  stain  in  the  dense  part  of  the 
experimental  plate,  and  increased  it  by  about  four 
times  in  the  lighter  portions.  The  entire  absence 
of  sulphite  in  another  part  of  the  same  plate  caused 
three  times  the  stain  in  the  denser  parts,  and  about 
five  times  in  the  lighter  parts,  as  compared  with 
that  portion  of  the  plate  developed  with  5 grains  to 
the  oz.  Alfred  Watkins  and  others  have  shown 
that  this  “ pyro-stain  ” has  an  important  influence  on 
the  printing  value  of  the  negative,  so  that  it  is 
better  to  use  sufficient  sulphite,  say  3 grams  to  the 
100  c.c.  or  15  grains  to  the  oz.,  to  practically  elimin- 
ate the  staining  altogether.  Some  photographers 
have  an  affection  for  the  yellow  stain,  and  think 
it  improves  the  “ quality  ” of  the  negative.  This 
may  be  true  in  cases  of  hard  negatives,  but  the 
photographer  should  have  complete  command  of  his 
plate  in  the  same  way  that  the  engine-driver  has  of 
the  various  levers  that  control  the  engine.  If  stain- 
ing is  allowed  to  creep  in,  the  result  becomes  largely 
a matter  of  chance.  For  the  same  reason,  the  photo- 
grapher should  understand  the  effect  of,  and  have 
under  his  command,  each  separate  constituent  of  his 
developer,  for  these  are  the  levers,  so  to  speak,  that 
control  the  photographic  negative. 


60 


ALKALIES  IN  DEVELOPMENT. 


Ammonia  solution  or  the  carbonate  of  sodium 
and  potassium  are  the  alkalis  employed  in  develop- 
ing with  pyrogallic  acid.  Ammonia,  although  it  is 
still  largely  used,  especially  by  professional  portrait 
photographers,  seems  unsatisfactory,  because  the 
ammonia  evaporates  from  the  solution  during 
development,  so  that  the  developer  grows  continually 
weaker  in  alkali ; the  original  concentrated  solution 
itself  is  always  varying  in  strength.  Besides  this,  it 
must  be  a very  bad  thing  for  other  plates  or 
sensitive  material  to  be  in  a room  reeking  with 
fumes  of  ammonia,  which  combine  with  any  acid 
fumes  that  may  be  about,  and  deposit  over  every- 
thing in  minute  crystals. 

Potassium  carbonate  possesses  no  advantage  over 
sodium  carbonate  except  that  it  is  much  more 
soluble,  which  is  an  advantage  in  making  up  very 
strong  solutions,  but  has  the  drawbacks  that  it  is 
much  dearer,  is  more  difficult  to  obtain,  and  more  of 
it  is  required  in  the  developer. 

Sodium  carbonate  is  the  most  convenient  alkali 
to  use.  Ordinary  washing  soda  is  the  form  generally 
employed,  but  there  are  two  other  forms  that  can 
be  used  equally  well,  namely,  the  monohydrated 
sodium  carbonate  and  dry  powdered  sodium 
carbonate.  The  former  of  these  two  has  recently 
been  introduced  commercially  so  that  it  is  well  to 
include  it.  The  latter  is,  or  should  be,  pure  sodium 
carbonate,  NagCOg.  The  following  table  gives  the 
equivalence  of  the  three  carbonates  to  one  another 


CAKBONATES  OF  SODA. 


61 


and  to  sodium  hydrate  (caustic  soda),  which  may  be 
useful  with  other  developers. 

TABLE  YIII. — Equivalence  between  Caustic  Soda 
AND  Carbonates  of  Soda. 


Dry  Sodium 
Carbonate. 

Monohydrated 
Sodium  Carbonate. 

Washing  Soda. 

Caustic  Soda. 

1 

1-17 

2-70 

0-76 

0-85 

1 

2-30 

0-64 

0-37 

0-43 

1 

0-28 

1*32 

1*55 

3-35 

i 1 

! 

It  is  convenient  to  know  that  bicarbonate  can  be 
converted  into  normal  (dry)  carbonate  of  sodium  by 
heating  it  strongly,  or  by  boiling  its  solution  for  some 
time.  Sixteen  parts  of  the  bicarbonate  are  equiva- 
lent to  ten  parts  of  the  ordinary  dry  carbonate. 

Increase  of  alkali  has  a strong  effect  in  hastening 
the  rate  of  development  all  over  the  plate,  excess 
causing  fog. 

Variations  in  the  quantity  of  the  pyrogallic  acid 
itself  are  important.  It  must  be  remembered  that 
excess  of  pyrogallic  acid  acts  as  a restrainer  unless 
the  alkali  is  increased  in  the  same  proportion.  In 
some  recent  experiments  the  author  has  found  that 
the  greatest  density  was  obtained  with  the  pyrogallic 
acid  and  alkali  in  proper  chemical  proportion  (2 
grains  “ pyro  ” to  7 grains  washing  soda).  Half  this 
quantity  of  pyro  (1  grain  to  the  ounce),  the  alkali 


62 


VARYING  THE  PYROGALLOL. 


remaining  the  same,  gave  less  than  half  the  density 
in  the  high  lights  of  the  negative,  and  only  one- 
fifth  or  one-sixth  in  the  shadows.  When  the  pyro 
was  increased  by  a half  {i.e.,  to  3 grains)  there  was 
a distinct  falling-off  in  the  density,  as  compared 
with  the  rightly  proportioned  developer,  to  three- 
quarters  in  the  high  lights,  and  about  the  same  in 
the  shadows.  When  the  pyro.  was  doubled  (i.e.,4: 
grains  to  the  ounce)  without  change  in  the  alkali, 
the  result  was  practically  the  same  as  if  one  grain 
to  the  ounce  had  been  used,  showing  the  strong 
restraining  action  of  the  pyrogallic  acid.  As  the 
shadows  were  restrained  more  in  proportion  than 
the  high  lights,  a considerable  excess  of  “ pyro  ” over 
alkali  is  clearly  an  advantage  in  developing  an  over- 
exposed plate.  The  effect  of  bromide  in  this 
direction,  however,  is  almost  the  same.  With  these 
experiments  in  varying  the  quantity  of  pyrogallic 
acid  in  the  developer,  it  was  found  that  the  yellow 
stain  did  not  increase  with  the  “ pyro  ” by  any 
means,  appearing  to  bear  little  relation  to  it,  but 
followed  the  density  of  the  silver  deposit  very  closely. 

As  regards  the  composition  of  the  developer, 
every  photographer  must  be  a law  unto  himself. 
The  developer  must  be  handled  according  to  the 
exposure  of  the  plate  and  the  result  the  worker 
desires  to  obtain.  The  formulae  given  by  plate 
makers  are,  as  a rule,  needlessly  complicated.  The 
following  is  a good,  sensible  formula,  which  will 
work  well  with  any  plate. 


PYROGALLIC  ACID  DEVELOPER. 


63 


Pyrogallic  acid,  . . ‘5  gram, 

Sodium  sulphite  (crystals),  4’0  „ 

Sodium  carbonate  (crystals),  1’5  ,, 

Potassium  bromide,  . . '25  „ 

Water  up  to  . . .100  c.c., 


2 

20 

7 

1 

1 


grains. 

jj 

j) 

oz. 


Unless  a large  number  of  negatives  are  to  be 
developed,  it  is  much  better  to  use  dry  pyrogallic 
acid,  weighing  out  sufficient  for  each  small  batch  of 
plates  before  commencing  development,  and  making 
it  into  a ten  per  cent,  solution.  The  other  materials 
may  also  be  used  conveniently  in  the  form  of  ten 
per  cent,  solutions.  The  quantities  to  be  taken  to 
make  up  the  above  developer  would  be : — 


Pyrogallic  acid  10%, 

. 5 c.c.. 

. 20 

minims. 

Sodium  sulphite  10%, 

. 40  „ 

. 160 

55 

Sodium  carbonate  10%, 

. 15  „ 

. 70 

55 

Potassium  bromide  10°/^, 

2|  „ 

. 10 

55 

Water  up  to  . 

100  „ 

1 

OZ. 

It  is  convenient,  as  a 

rule,  to  add  half 

the  alkali 

at  the  beginning  and  the  remaining  half  as  ex- 
perience dictates.  If  the  sky  and  high  lights  appear 
to  be  growing  too  dense,  the  full  quantity,  and  even 
an  excess,  of  alkali  should  be  added  immediately. 

In  the  following  formula  ammonia  takes  the 
place  of  sodium  carbonate,  ammonium  bromide  being 
used  instead  of  potassium  bromide. 


Pyrogallic  acid,  . . *25  gram, 

Sodium  sulphite,  . P2  „ 

Ammonium  hydrate,  ( 

Liquor  ammonise  '880)  j 
Ammonium  bromide,  ’25  gram, 
Water  up  to  . . 100  c.c., 


1 grain. 

2*5  minims. 

1 grain. 

1 oz. 


64 


STOCK  SOLUTIONS. 


Ten  per  cent,  solutions  may  be  used  as  recom- 
mended in  the  previous  formula.  When  large 
quantities  are  required,  the  sulphite  and  the  pyro- 
gallic  acid  may  be  incorporated  into  one  stock 
solution  in  the  proportion  of — 

Pyrogallic  acid,  50  grains,  . . 1 oz.  (avoir.). 

Sodium  sulphite,  250  „ . • 5 ,,  „ 

Water  up  to  . 1000  c.c.,  • 20  „ „ 

For  use  take  20  minims  of  the  stock,  4 drams  of 

10°/o  ammonia,  and  10  minims  of  10%  ammonium 
bromide  with  water  to  make  up  one  ounce.  If  a 
stronger  developer  is  required,  all  the  constituents 
may  be  increased  in  the  same  proportion.  Nearly 
all  the  remarks  made  in  connection  with  the 
sodium  carbonate  developer  apply  to  the  one  just 
recorded. 

When  making  up  stock  solutions  of  pyrogallic 
acid,  ferrous  sulphate,  or  any  easily  oxidizable 
materials,  it  is  a good  plan  to  use  the  arrangement 
figured  on  page  65,  whether  a burette  is  employed  or 
not.  But,  as  every  time  a quantity  of  liquid  is 
drawn  off  from  the  large  containing  vessel  the  same 
volume  of  air  enters,  it  is  necessary  to  put  in  an 
oxygen  trap,  as  shown  in  fig.  5. 

Either  a small  bottle  can  be  used  or  a glass  bulb 
intended  for  the  purpose  can  be  purchased  at  a 
chemical  dealer’s.  The  bottle  or  bulb  contains  an 
inch  or  so  of  strong  pyrogallic  acid  and  soda  in  the 


OXYGEN  TRAPS. 


65 


same  proportions  as  used  in  the  developer  ; this 
arrangement  will  last  for  a year  or  more  without 
being  renewed.  If  the  oxygen  trap,  etc.,  is  not 
available  do  not  put  the  whole  stock  into  one 
stoppered  bottle,  as  is  generally  recommended ; but 


fill  a number  of  small  corked  bottles  with  the 
solution,  cork  them  tightly,  melt  up  some  paraffin 
candle  ends  in  an  iron  ladle  or  something  of  the 
kind,  and  dip  the  tops  of  the  bottles  in  the  melted 
paraffin  to  render  them  air-tight.  Stock  solution 
treated  like  this  will  keep  indefinitely,  and  no 
preservative,  such  as  citric  acid,  is  required,  as 
there  is  no  large  air  space  above  the  solution  to 
make  it  go  wrong. 


E 


66 


HYDKOQUINONE. 


Hydroquinone  works  more  slowly  than  pyrogallic 
acid.  For  that  reason  there  is  less  tendency  to 
fog  the  plate  during  the  prolonged  development 
necessary  for  under-exposed  plates,  for  which  hydro- 
quinone developer  is  very  suitable.  Although  an 
excellent  developer,  there  does  not  seem  to  be  so 
much  control  over  the  plate  as  with  pyrogallic  acid. 

The  following  is  a good  formula,  giving  a choice 
of  either  sodium  hydrate  or  carbonate ; the  former 
is  to  be  preferred.  Except  in  cases  of  over-ex- 
posure for  which  hydroquinone  is  not  satisfactory, 
the  bromide  may  be  left  out. 

Hydroquinone,  . . . *8  gram,  . 4 grains. 

Sodium  sulphite  (crystals),  3‘5  „ .16  „ 

Citric  acid,  . . . . '05  „ . | „ 

Potassium  bromide,  . . '2  „ . 1 „ 

f Caustic  soda,  . . . '4  „ . 2 „ 

4 or 

[ Sodium  carbonate  (crystals),  3*0  „ .15  „ 

Water  up  to  . . 100  c.c.,  . 1 oz. 

Caustic  soda  is  an  inconvenient  material  to  weigh 
out  in  small  quantities,  so  that  it  will  be  better  to 
make  up  a stock  of  10%  solution.  The  rest  of  the 
materials  can  be  made  up  into  a solution  double 
the  strength  in  the  formula,  thus : — 

A.  Hydroquinone,  . 16  grams,  . 160  grains. 

Sodium  sulphite, . 70  ,,  . IJ  ozs. 

Citric  acid,  . . 1 „ . 20  grains. 

Potassium  bromide,  4 ,,  .40  „ 

Water  up  to  1000  c.c.,  . 20  ozs. 


EIKONOGEN. 


67 


B.  Caustic  soda  10°/o  solution,  80  c.c.,  If  ozs. 
or 

Sodium  carbonate  107o  ” 

Water  up  to  . . . 1000  „ 20  „ 

For  use  take  equal  parts  A and  B.  The  same 
quantity  of  water  may  be  added  with  advantage 
if  the  plate  is  not  under-exposed.  The  strong 
alkali  used  in  this  developer  is  liable  to  cause 
frilling. 

Eikonogen  is  a complicated  organic  sodium  salt 
(see  index).  It  is  not  a convenient  developer 
to  use,  as  it  dissolves  in  water  with  difficulty 
and  deteriorates  rapidly  when  it  has  dissolved. 
Its  action  is  very  powerful,  however,  and  many 
workers  use  it  for  developing  snap-shots,  lantern 
slides,  and  badly  under-exposed  plates.  The  follow- 
ing formula  is  recommended  : — 

A.  Eikonogen,  . . .5  grams,  24  grains. 

Sodium  sulphite,  . . 20  „ 96  „ 

Water  up  to  . . 300  c.c.,  3 ozs. 

B.  Sodium  carbonate  (crystals),  15  grams,  70  grains. 

Water  up  to  . . 100  c.c.,  1 oz. 

For  use  take  3 of  A to  1 of  B immediately 
before  developing.  It  is  not  advisable  to  make  up 
more  than  is  required  for  immediate  use.  Bromide, 
if  used  at  all,  must  be  introduced  very  sparingly. 
For  very  under-exposed  plates,  the  following  may 
be  used  instead  of  B : — 

Caustic  soda  10°/^,  ...  50  c.c.,  | oz. 

Water  up  to  . . . . 100  ,,  1 „ 


68 


METOL. 


MetoP  possesses  a marked  effect  in  bringing  out 
detail  in  under-exposed  plates,  and  a mixture  of 
this  with  hydroquinone  is  perhaps  even  more 
effectual. 

It  is  an  excellent  developer,  being  preferred  by 
many  people  to  pyrogallic  acid.  The  following  is 
a good  formula : — 


Metol,  . . . . *8  grams, 

Sodium  sulphite  (crystals),  . 5’5  „ 

Sodium  carbonate  (crystals),  4*5  „ 

Potassium  bromide,  . . *2  ,, 

Water  up  to  . , 100  c.c., 


4 grains. 


24 

20 

1 

1 


5> 


J) 

oz. 


It  is  well  to  dissolve  the  metol  first  and  then 
add  the  other  constituents.  Some  people  are  very 
sensitive  to  the  action  of  metol,  which  sets  up 
violent  inflammation  in  their  hands. 

Amidol  is,  chemically  speaking,  di-amido-phenol 
or  pyrogallic  acid  in  which  two  of  the  OH’s  are 
replaced  by  NHg.  This  last  is  derived  from 
ammonia,  NHg,  in  the  same  way  that  OH  is  derived 
from  water,  OHg,  and  plays  a very  important  part 
in  organic  chemistry.  - 


Pyrogallic  acid. 


CaH 


3 


OH 

OH 

OH 


Di-amido-pbenol  (amidol). 


C0H3 


NH2 

NH^ 

OH 


It  is  a powerful  reducing  agent,  and  has  the 


For  chemical  formula  see  index. 


AMIDOL. 


69 


peculiarity  of  working  without  an  alkali.  The 
image  comes  up  very  quickly  when  using  amidol, 
and  care  must  be  taken  to  leave  the  plate  in  the 
developer  until  it  has  attained  sufficient  density. 
Amidol  dissolves  more  readily  in  a solution  of  sul- 
phite than  in  water,  and  sulphite  has  an  accelerating 
action  with  this  developer.  Amidol  keeps  very 
badly,  and  it  is  advisable  to  make  up  fresh  solution 
for  each  batch  of  plates.  It  is  not  easy  to  restrain 
this  developer,  as  bromides  do  not  seem  very  effectual 
with  it.  The  presence  of  a small  quantity  of 
bromide,  however,  (say  1 drop  of  a 10°/o  solution 
to  each  ounce  of  developer)  prevents  any  tendency 
to  fog. 

Amidol,  . . . . ’5  grams,  . 2^  grains. 

Sodium  sulphite  (crystals),  3*0  „ .15  „ 

Water  up  to  . . . 100  c.c.,  . 1 oz. 

In  case  of  under-exposure,  add  1 c.c.  to  each  100 
c.c.,  or  5 or  six  drops  to  each  oz.  of  a 10°/o  solution 
of  sodium  carbonate  crystals,  and  the  same  quantity 
of  potassium  bromide. 

Paramido-phenol  is  hydroquinone  in  which  one 
OH  has  been  replaced  by  NHg. 


Hydroquinone. 
p TT  / OH 
I OH 


Paramido-phenol. 


OH 

NR, 


Its  hydrochloride,  or  compound  with  hydrochloric 
acid  (C6H4.OH.NH2.HCl),  is  usually  employed  and 
is  sold  in  solution  as  “ Eodinal,”  which  keeps 


70 


EODINAL,  GLYCIN. 


excellently.  Those  who  use  it  speak  very  highly 
of  it  as  an  all  round  developer,  and  the  author  has 
obtained  good  results  with  it  in  radiography.  It 
is  convenient  to  make  up  a strong  solution,  similar 
to  rodinal,  and  dilute  it  when  required. 

Strong  solution — 

Paramido-phenol  hydrochloride,  *5  grams,  25  grains. 

Sodium  sulphite,  . . .9  „ 1 oz. 

Sodium  carbonate  (crystals),  .9  „ 1 „ 

Water  up  to  . . . 100  c.c.,  . 10  ozs. 

For  use,  take — 

Strong  solution  (Rodinal),  . . 10  c.c.,  1 oz. 

Potassium  bromide  10°/o  solution,  . 2 „ J „ 

Water  up  to  . . . . 100  „ 10  „ 

Glycin*  gives  hard,  sharp  negatives,  and  acts 
slowly.  It  is  useful,  therefore,  in  copying  line 
drawings  and  similar  subjects,  and  works  well  with 
kinematograph  films.  Glycin  is  rather  insoluble  by 
itself,  but  dissolves  readily  in  alkali  and  sulphite. 
The  following  is  a good  formula : — 

Glycin,  ....  *8  grams,  . 4 grains. 


For  convenience,  it  may  be  made  up  four  times 
this  strength  and  diluted  for  use. 

o 


Sodium  sulphite  (crystals),  2 
Sodium  carbonate  (crystals) 
Water  up  to 


I 


. 10 
. 15 


1 oz. 


* For  chemical  formula  see  index. 


HYDROXYLAMINE. 


71 


Hydrazine  (N2H4)  and  hydroxylamine  (NH2.OH) 
have  been  proposed  as  developers,  the  latter  by 
Spiller  and  Egli.  They  are  only  of  scientific  in- 
terest, however. 

As  regards  the  majority  of  these  developers,  it 
is  difficult  to  say  that  one  is  better  or  worse  than 
another.  The  best  (feveloper  is  undoubtedly  the 
developer  that  suits  the  photographer’s  particular 
method  of  exposing,  developing,  and  printing.  The 
same  dictum  applies  to  the  various  formulse,  which 
must  not  be  taken  as  absolute,  but  merely  as 
general  guides,  to  be  varied  according  to  circum- 
stances. 

Before  closing  the  subject  of  development,  atten- 
tion must  be  paid  for  a few  moments  to  the  work  of 
Hurter  and  Driffield,  whose  results  are  quite  easy  to 
understand.  In  a perfect  negative,  containing  only 
black  and  white  and  no  yellow  stain,  you  have  minute 
black  spots  on  a transparent  ground.  Supposing 
you  had  a small  plate,  say  one  inch  each  way,  and 
you  divided  it  by  cross  lines  into  ten  thousand  equal 
squares  and  then  stopped  up  nine  thousand,  so  that 
no  light  could  come  through  these  particular  squares, 
you  would  have  something  that  would  represent 
roughly  a photographic  negative.  If  you  put  this 
in  a printing  frame  against  the  light,  only  one-tenth 
of  the  light  falling  on  the  plate  would  come  through. 
Supposing  another  similar  plate  were  placed  behind 
the  first  plate,  it  would  pass  one -tenth  of  the  light 
that  had  filtered  through  the  first  plate,  one- 


72 


HURTEK  AND  DRIFFIELD 


tenth  of  one-tenth  of  the  original  light.  The  light 
coming  through  a third  similar  plate  would  he  one- 
tenth  of  one-tenth  of  one- tenth  of  the  original,  and 
so  on.  That  is  to  say,  the  light  coming  through  each 
of  the  three  plates  would  be  -^th, 
etc.,  of  the  original,  or  taking  it  the  reverse  way,  the 
ratios  between  the  lights  w^ld  be  10,  100,  1000, 
etc.  Now  the  logarithms  of  10,  100,  1000,  etc.,  are 
1,  2,  3,  and  so  on  ; so  that  the  logarithm  of  the 
light  stopped  by  one  screen  or  one  density  is  1,  by 
two  screens,  2,  by  three  screens,  3,  etc.  Supposing 
you  want  to  photograph  a scale  of  tones  so  graded 
that  they  are  in  the  order  1,  2,  3,  4.  A correct 
result  will  only  be  obtained  if  the  printing  values  of 
the  different  parts  of  the  negative  are  1, 2,  3, 4 ; that 
is  to  say,  “ each  density  must  be  proportional  to  the 
logarithm  of  the  light  intensity  that  produced  it.” 
By  experiment  Hurter  and  Driffield  found  that  for 
every  plate  there  was  a particular  exposure,  within 
the  limits  of  which  this  law  held  good ; above  and 
below  these  limits  the  ratios  were  false.  More  than 
this,  they  found  that  the  gradation  in  a negative, 
developed  with  ferrous  oxalate,  could  not  be  altered 
by  any  amount  of  development,  supposing  no  fog  was 
introduced,  but  depended  entirely  on  the  exposure. 

On  this  was  based  the  H and  D system  of  deter- 
mining the  sensitiveness  of  plates. 

The  plate  receives  exposures  from  a standard  light 
graduated  from  2^,  5,  10,  20,  40  to  160  secs.,  the  first 
portion  of  it,  called  the  “ fog  strip,”  receiving  no  ex- 


SPEED  MEASUREMENT. 


73 


posure  at  all.  This  plate  is  developed  in  the  standard 
developer  for  a standard  time  at  a standard  tempera- 
ture (see  p.  54),  and  the  densities  of  the  different 
strips  are  read  on  a photometer,  and  recorded  in  the 
manner  shown  below  (fig.  6).  The  bottom  line  of 


Fig.  6. — Speed  readings  of  two  plates — A,  ordinary  ; B,  rapid. 


the  chart  represents  the  logarithms  of  the  exposures, 
and  the  upright  line  the  densities  read  on  the  photo- 
meter, the  density  of  the  fog  strip  being  subtracted 
from  each  one.  It  will  be  noticed  that  several  of 
the  dots  are  in  a straight  line ; this  is  the  period  of 
correct  exposure.  The  straight  line  is  prolonged  to 
meet  the  base  line,  and  the  number  read  off,  which 
gives  the  “ inertia  ” of  the  plate,  or  the  exposure 


74 


INFLUENCE  OF  PYRO-STAIN. 


correctly.  To  obtain  the  H and  D speed  number, 
the  figure  where  the  straight  line  cuts  the  base  is 
read  off,  and  this  divided  into  34  gives  the  speed 
number  required. 

' The  important  points  brought  out  by  Hurter  and 
Driffield,  in  addition  to  the  accurate  method  of 
determining  the  speed  of  plates,  are  first,  that  the 
gradation  in  a negative  cannot  be  altered  during 
development,  unless  fog  or  stain  is  introduced ; and 
secondly,  that  pyro-ammonia  is  a very  uncertain  de- 
veloper. Another  point  arises  out  of  the  former  one, 
namely,  that  sensitiveness  of  the  plate  is  as  much 
a matter  of  the  developer  used  as  of  the  state  of 
the  emulsion  itself,  the  speed  number  of  the  plate 
developed  with  pyro-soda  being  much  higher  than 
when  developed  with  ferrous  oxalate,  and  the  speed 
number  with  metol,  for  instance,  is  higher  still. 

The  Hurter  and  Driffield  system,  as  has  been 
pointed  out,  takes  no  account  of  the  yellow  stain 
produced  by  development  with  pyrogallic  acid  and 
other,  organic  developers.  Alfred  Watkins  and 
others  have  given  considerable  attention  to  this 
matter,  and  have  shown  that  the  “ pyro  stain  ” has 
an  important  influence  on  the  printing  value  of  the 
negative.  This  pyro-stain  is  something  more  than 
a mere  stain,  for  if  the  silver  be  dissolved  out  of  the 
plate  with  nitric  acid,  a faint  yellow  image  remains. 
Light,  oxidising  agents,  tannin,  and  other  agents 
cause  gelatin  to  become  insoluble.  This  is  probably 
the  explanation  of  the  pyro-image.  Various  agents 


TANNING  OF  GELATIN. 


75 


first  action  of  the  cyanide  is  to  form  insoluble  silver 
are  present,  such  as  the  oxidized  pyrogallic  acid 
which  resembles  tannin  in  some  respects,  and  the 
nascent  compounds  set  free  when  the  silver  bromide 
is  reduced,  whilst  the  action  of  the  light  itself  on  the 
gelatin,  and  other  little  known  causes,  are  at  work  to 
“ tan  ” the  gelatin.  Wherever  the  gelatin  becomes 
insoluble, — and  this  is  most  likely  to  happen  where 
the  chemical  action  of  building  up  the  silver  image 
is  taking  place, — it  fixes  some  of  the  highly  coloured 
products  of  the  oxidation  of  the  pyrogallic  acid  or 
other  phenolic  developer. 

As  regards  the  “ tanning  ” of  the  gelatin  or 
rendering  it  insoluble,  formaldehyde  (see  p.  76)  has 
a strong  action  and  is  used  to  prevent  plates  frilling 
in  hot  weather.  Plates  washed  with  formaldehyde 
may  be  dried  by  means  of  heat,  that  could  not  be 
applied  in  the  ordinary  way  without  melting  the 
gelatin.  Formaldehyde  is  supplied  commercially  in 
40  per  cent,  solution.  This  should  be  diluted  as 
follows,  and  the  plate  should  be  immersed  for  ten 
minutes,  being  well  washed  afterwards  : — 

Formaldehyde  (40°/^  solution),  . . 1 part. 

Water,  . . . . . .3  parts. 

Following  up  the  work  of  Schwartz  and  Mercklin, 
and  of  Hellheim,  Messrs.  Lumiere  and  Seyewitz 
have  found  that  formaldehyde  is  not  the  only  alde- 
hyde capable  of  tanning  gelatin.  Aldehydes  add  to 
the  reducing  power  of  the  developer,  but  only  in 


76 


FORMALDEHYDE,  ACETONE. 


required  before  the  plate  commences  to  register 
effect  to  aldehydes,  and  can  be  used  advantageously 
to  take  the  place  of  the  alkali.  With  pyrogallic 
acid,  development  is  effected  rapidly;  with  hydro- 
quinone,  the  development  is  not  so  rapid,  but  the 
results  are  as  vigorous  as  with  alkaline  carbonates. 
Lumiere  and  Seyewitz  find  that  the  addition  of 
formaldehyde  (formalin)  to  the  developer  causes 
strong  staining  of  the  film,  with  the  exception  of 
paramido-phenol  (rodinal)  and  metol  developers.  The 
following  are  the  formulae  proposed  for  development 
with  acetone  and  sulphite  in  place  of  an  alkali : — 


A.  Pyrogallic  acid,  . . 1 ’8  grams,  9 grains. 

Water,  . . . 100  c.c.,  1 oz. 

Sulphite  of  soda  (crystals),  1 1 grams,  56  grains. 
Acetone,  . . . 2 ’5  c.c.,  12  minims. 


B.  Hydroquinone, 
Sulphite  of  soda, 
Acetone, 

Water,  . 


. 3 

. 20 
. 10 
100 


grams,  15  grains. 
„ 100  „ 


C.C.,  50  minims. 


jj 


1 oz. 


When  the  plate  has  been  developed  to  the  right 
density,  it  is  washed  carefully  under  the  tap,  and 
allowed  to  soak  for  a few  minutes  in  water ; then  it 
is  fixed,  i.e.,  the  unaltered  silver  salts  are  dissolved 
out  of  the  film,  so  as  to  leave  no  material  sensitive 
to  light  on  the  plate.  The  principal,  and  practically 
the  only,  substances  used  for  this  purpose  are 
potassium  cyanide  and  sodium  thiosulphate  (“  hypo  ”). 
The  action  of  the  two  solvents  is  very  similar : the 


FIXING. 


77 


cyanide  by  double  decomposition  with  the  silver 
bromide,  and  then  to  make  a double  silver  potassium 
cyanide,  which  is  soluble  in  water. 

Potassium  Silver  Silver  Potassium 

cyanide.  bromide.  cyanide.  bromide. 

(1)  KCN  + AgBr  = AgCN  + KBr. 

(2)  KCN  + AgCN  = KCN,AgCN. 

With  thiosulphate,  silver  thiosulphate  is  first 
formed,  and  then  a double  soluble  thiosulphate  of 
silver  and  sodium. 

Sodium  Silver  Silver  Sodium 

thiosulphate.  bromide.  thiosulphate.  bromide. 

(1)  ^28203  + 2AgBr  = Ag2S203  + 2NaBr. 

(2)  Ag2S203  + Na2S203  = Ag2S203  , Na2S203. 

The  quantity  of  potassium  cyanide  to  be  used  will 
be  found  under  the  development  of  wet  plates  (p.  41, 
which  see).  Of  sodium  thiosulphate,  solutions  vary- 
ing from  40  to  10  of  the  crystals  in  100  of  water 
can  be  used,  the  former  for  negatives  and  the  latter 
for  prints.  Haddon  and  Grundy  have  shown  that 
10  per  cent,  is  the  best  strength  for  fixing  prints  on 
albumenized  paper.  It  is  well  to  employ  a saturated 
solution  of  the  salt  (50  per  cent.),  and  dilute  just 
before  starting  development. 

Acids  decompose  sodium  thiosulphate  into  sul- 
phurous anhydride  (sulphurous  acid  gas,  or  burnt 
sulphur)  and  free  sulphur.  The  reader  should  try 
the  experiment  of  adding  a little  hydrochloric  acid 
to  a little  solution  of  sodium  thiosulphate.  In  a 
few  moments  he  will  be  able  to  smell  the  burnt 


78 


ACID  THIOSULPHATE. 


the  presence  of  sulphite.  Acetone  has  a similar 
sulphur,  and  will  see  the  liquid  turn  milky  with 
free  sulphur,  thus — 


+ 2HC1  = 2NaCl  + H2O  + 


Sulphurous  acid  has  a very  strong  bleaching  action 
and  the  sulphur  is  liable  to  cause  stains.  Acid  or 
alum,  which  contains  free  acid,  should  never  be 
added  to  the  fixing  bath. 

As  soon  as  the  fixing  bath  begins  to  work  slowly 
it  should  be  thrown  out  and  a fresh  lot  made  up. 
Exposure  to  the  air  gradually  oxidizes  the  thio- 
sulphate and  sets  up  decomposition.  Old  baths  full 
of  dirt  and  pyro-stains  should  not  be  used,  as  they 
are  almost  certain  to  bleach  or  discolour  the  negative 
or  print. 

As  regards  the  washing  of  negatives  free  from 
thiosulphate  after  fixing,  the  reader  is  referred  to 
page  14. 


Sodium  Hydrochloric  Sodium 

thiosulphate.  Acid.  chloride. 


Water. 


Sulphurous 

anhydride. 

so. 


Sulphur. 

+ s. 


POSITIVE  AND  NEGATIVE. 


79 


CHAPTEK  V. 

Keveksal. 

In  one  sense  it  is  largely  accidental  that  a 
“ negative  ” is  produced  by  the  ordinary  method  of 
exposure  and  development.  If  a piece  of  paper  be 
coated  with  ferric  oxalate  and  exposed  in  the 
camera,  the  reduced  image  will  be  lighter  than  the 
unreduced,  that  is  to  say,  a positive  will  be  produced. 
If  this  be  washed  over  with  ferricyanide  of 
potassium,  the  positive  will  be  converted  into  a 
negative  ; if  ferrocyanide  had  been  used,  the  positive 
would  have  remained  positive. 

All  chemical  reactions  are  reversible,  given  proper 
conditions.  In  a mixture  of  substances  such  as 
exists  in  the  film  of  a sensitive  plate,  where  there 
is  no  outlet  for  the  products  of  decomposition — the 
excess  of  bromime  or  other  halogen  set  free  on 
reduction  in  this  case — a state  of  equilibrium  is 
reached  at  a certain  point.  If  decomposition  is 
carried  beyond  this  point,  reversal  sets  in,  which 
may  go  the  whole  way  until  the  original  compounds 
are  re-formed. 


80 


REVERSAL. 


This  occurs  in  actual  practice  in  photography. 
When  a plate  is  over-exposed  the  high  lights  are 
thin  after  development,  i.e.,  partial  reversal  has 
taken  place.  By  great  over-exposure  reversal  can 
be  carried  to  such  an  extent  that  a positive  is 
obtained  instead  of  a negative.  This  process  is 
actually  employed  for  copying  negatives  without 
going  to  the  trouble  of  making  a transparency  and 
printing  from  that  again.  The  resulting  negative  is 
reversed  as  regards  right  and  left,  which  is  a draw- 
back if  needed  for  ordinary  photographic  printing, 
though  it  is  an  advantage  in  many  “ process  ” applica- 
tions. 

The  actual  method  of  accomplishing  this,  due  to 
T.  Bolas,  is  as  follows : — Soak  a gelatino-bromide  dry 
plate  for  five  minutes  in  a 4 per  cent,  solution  of 
bichromate  of  potassium,  rinse  once  or  twice,  and 
then  dip  into  a bath  of  equal  parts  of  methylated 
spirit  and  water.  Blot  off  the  superfluous  moisture 
and  allow  the  plate  to  dry,  all  these  operations 
being  conducted  in  the  dark  room.  Then  expose 
the  plate  in  a printing  frame  behind  the  original 
negative,  and  expose  to  direct  sunlight  for  three  or 
four  minutes.  On  removal  from  the  frame  in  the 
dark  room  a faint  image  will  be  seen  on  the  plate, 
which  is  developed  and  fixed  as  usual.  A chloride 
plate  must  not  be  used  for  this  purpose,  as  the  re- 
duction of  silver  chloride  cannot  be  reversed  in  the 
same  way  as  silver  bromide. 

Several  chemicals  have  the  power  of  reversing  a 


HALATION. 


81 


plate  in  a similar  manner  to  light.  Sodium  hypo- 
phosphite  has  this  peculiarity.  The  organic  substance 
thiosinamine  and  the  organic  salts  known  as  thiocar- 
bamides  when  added  to  the  developer  have  this 
effect.  Colonel  J.  Waterhouse  recommends  for  this 
purpose  the  following  developer  : — 

A.  Lithium  carbonate  saturated 

solution,  . . 100  C.C.,  . 1 oz. 

Eikonogen,  . . 1 gram,  . 5 grains. 

Sodium  sulphite,  . 1 „ -5  ,, 

Dissolve  the  two  latter  in  the  first  just  before  using, 
and  add  a few  drops  of 

B.  Ammonium  bromide,  . . .1  part. 

Thiocarbamide,  . . . .3  parts. 

Dissolved  in  water  (quantity  not  stated). 

“ Solarization  ” is  the  word  usually  employed  to 
denote  the  local  reversals  that  sometimes  occur  on 
plates  containing  very  strong  contrasts.  “ Halation  ” 
or  the  veiling  or  blurring  of  the  edges  of  the  high 
lights,  such  as  the  sky-lines  of  houses  or  the 
branches  of  trees  taken  against  the  light,  is  a species 
of  partial  reversal,  generally  attributed  to  reflection 
from  the  back  of  the  plate.  To  prevent  this  it  is 
usual  to  “ back  ” the  plate  with  some  non-actinic 
medium,  such  as  caramel  and  burnt  sienna.  The 
following  formula,  due  to  J.  S.  Teape,  is  a good 
one : — 

Boil  1 lb.  of  white  lump  sugar  in  a saucepan  large 
enough  to  hold  twice  the  bulk,  for  one  hour  after  it  has 

F 


82 


BACKING  PLATES. 


melted,  stirring  with  a wooden  rod  the  whole  time. 
Allow  the  liquid  to  cool  slightly,  then  add,  in  small 
quantities  at  a time,  4 ounces  of  hoiling  water,  and  stir 
between  each  addition. 

Of  this  caramel  take  . . • 

Saturated  solution  of  gum  tragacanth,  1 oz. 
Powdered  burnt  sienna,  . . 2 ozs. 

Methylated  spirit,  . . . 2 ,, 

Add  the  spirit  after  the  other  ingredients  are  well 
mixed.  Apply  thinly  to  back  of  plate  by  dabbing  with 
flat  hog’s-hair  brush. 

Instead  of  making  the  caramel  from  the  sugar,  it 
can  be  purchased ; the  dry  powdered  form  is  the 
best. 

Some  recent  work  of  the  author’s  seems  to  show 
that  the  caramel  alone  is  sufficient  to  stop  halation, 
and  that  the  following  formula  is  satisfactory : — 


White  starch  or  flour. 
Caramel  powder. 

Sodium  carbonate  (crystals). 
Methylated  spirit. 

Water,  . . . . 


10  parts. 


10 

2 

25 

75 


}> 

jj 

>5 

}J 


Boil  the  water  first ; mix  the  starch  into  a thin 
paste  with  part  of  the  water  (cold)  and  pour  into 
the  boiling  water ; then  add  the  caramel  and,  when 
thoroughly  incorporated  and  cold,  the  spirit. 


FEREICYANIDE  REDUCTION. 


83 


CHAPTEK  VI. 

Eeduction,  Intensification,  etc. 

If  the  image  in  the  negative  is  too  dense,  it  is 
sometimes  necessary  to  reduce  its  intensity.  Any 
per-chloride,  such  as  per-chloride  of  iron,  or  similar 
salt,  will  have  the  effect  of  converting  the  silver  of 
the  image  into  chloride.  This  must  be  associated 
with  an  agent,  such  as  thiosulphate  of  soda,  which  is 
capable  of  dissolving  the  silver  chloride  as  it  is 
produced,  otherwise  it  would  be  difficult  to  know 
when  the  reduction  had  proceeded  far  enough. 
The  method  generally  used  in  practice  is  that  of 
Howard  Farmer,  in  which  a mixture  of  potassium 
ferricyanide  and  sodium  thiosulphate  is  employed. 
The  action  is  very  simple,  silver  ferricyanide  being 
produced,  which  dissolves  in  the  thiosulphate. 
The  reducing  mixture  should  be  made  up  in  small 
quantities  at  a time,  as  the  thiosulphate  slowly 
reduces  the  ferricyanide,  rendering  the  mixture 
useless.  The  negative  should  be  soaked  in  water 


84 


INTENSIFICATION. 


for  ten  minutes,  and  then  be  placed  in  a 12^ 
solution  of  sodium  thiosulphate  to  which  a certain 
quantity  of  10%  solution  of  potassium  ferricyanide 
has  been  added ; the  amount  can  be  regulated 
according  to  the  rapidity  of  reducing  action  re- 
quired. All  the  hypochlorites  act  on  the  silver 
image  and  can  be  used  to  reduce  its  density. 

Intensification  is  very  commonly  employed, 
especially  in  wet  plate  negatives.  All  the  methods 
employed  have  for  their  object  the  conversion  of 
the  particles  of  silver  into  some  compound  that 
will  increase  the  printing  value.  With  the  ex- 
ception of  a few  cases,  the  image  is  first  bleached 
with  mercuric  chloride,  which  converts  the  black 
silver  image  into  a white  double  silver-mercurous 
chloride.  This  must  be  washed  carefully  before 
proceeding  to  the  next  stage,  and  it  is  absolutely 
necessary  to  success  in  intensification  that  the 
film  be  thoroughly  cleansed  from  “ hypo.”  Mr 
Chapman  Jones  has  done  a great  deal  of  valuable 
work  on  intensification.^  He  finds  that  the  old 
method  of  treating  the  bleached  plate  with  ferrous 
oxalate  developer  is  by  far  the  most  reliable 
method.  The  plate  is  first  of  all  treated  to  a bath 
of  dilute  hydrochloric  acid  containing  one  part  in 
one  hundred  and  is  then  soaked  in 

Per-chloride  of  mercury,  . . 2 parts. 

Water, ......  100  „ 

* See  Royal  Photographic  Society's  Journal,  June  1897,  and 
earlier  issues. 


VAEIOUS  INTENSIFIERS. 


85 


until  thoroughly  bleached.  After  well  washing, 
the  plate  is  placed  in  a bath  of  ordinary  ferrous 
oxalate  developer  (which  see)  until  quite  black, 
when  it  is  again  washed.  If  not  sufficiently 
intensified  the  whole  operation  may  be  repeated 
a second,  and  even  a third  time,  the  chemical 
effect  being  to  form  an  amalgam  of  silver  and 
mercury,  which,  through  the  pt'otection  afforded  by 
the  gelatin,  is  permanent. 

A very  common  method  is  to  treat  the  bleached 
plate  with  very  dilute  ammonia.  The  action  in 
this  case  is  very  complicated,  as  the  black  intensi- 
fied image  consists  principally  of  uncertain  com- 
pounds of  ammonia  and  mercury,  the  silver  being 
largely  dissolved  out.  Consequently,  the  effect  on 
the  plate  is  by  no  means  uniform,  the  thinner  parts 
being  actually  reduced  by  the  solvent  action  just 
referred  to.  If  employed,  the  ammonia  solution 
should  contain  about  ten  drops  of  liquor  ammonia 
•880  to  the  ounce. 

Sulphite  of  soda  can  be  used  after  bleaching  with 
mercury,  but  the  intensifying  action  is  not  very 
strong  or  certain.  The  chemical  effect  is  to  reduce 
part  of  the  silver  and  mercury  to  the  metallic  state, 
and  to  dissolve  part  as  sulphites. 

A mixture  of  potassium  iodide  and  potassium 
cyanide  is  sometimes  applied  to  the  bleached  plate. 
It  is  uncertain  in  its  action,  and  changes  take 
place  on  storing,  as  they  do  with  plates  blackened 
by  ammonia.  The  same  applies  to  a mixture  of 


86 


SILVER  AND  LEAD  INTENSIFIERS. 


silver  nitrate  and  potassium  cyanide  sometimes 
employed. 

Wet  plates  are  frequently  intensified  by  silver 
nitrate  mixed  with  an  acid  developer,  such  as  pyro- 
gallic  acid  containing  citric  acid,  the  following  being 
employed  at  the  Bolt  Court  Process  School : — 


A.  Silver  nitrate. 
Water  distilled,  . 


22*8  grams, 
1000  C.C., 


B.  Pyrogallic  acid,  . 11*4  grams. 

Citric  acid,  . 28'5  „ 

Water  distilled,  . 1000  c.c., 


200  grains. 
20  ozs. 


100  grains. 
250  „ 

20  ozs. 


Perricyanides  of  uranium  and  lead  are  occasion- 
ally used,  the  action  being  to  form  an  insoluble 
ferrocyanide.  It  is  therefore  very  important  that 
in  making  the  solution  the  crystal  of  ferricyanide  of 
potassium  be  washed  free  from  any  adhering  ferro- 
cyanide. The  uranium  ferrocyanide  is  red  in  colour, 
and  is  very  opaque  to  the  rays  causing  photographic 
action,  so  that  care  must  be  taken  not  to  over- 
intensify. The  lead  ferrocyanide  is  white,  and  must 
be  treated  with  ammonium  sulphide,  which  turns  it 
into  black  sulphide  of  lead.  Instead  of  the  ferri- 
cyanides  of  lead  or  uranium,  a mixture  of  potassium 
ferricyanide  and  lead  or  uranium  nitrate  is  used. 


Lead  Intensifier. 


Lead  nitrate,  . . 4 grams. 

Potassium  ferricyanide,  6 ,, 

Acetic  acid  (glacial),  2 c c., 

Distilled  water  up  to  100  ,, 


. 20  grains. 

. 30  „ 

. 10  minims. 
. 1 oz. 


LEAD  AND  UEANIUM. 


87 


Uranium  Intensijier. 


Uranium  nitrate,  . . 1 gram, 

Potassium  ferricyanide,  .1  ,, 

Acetic  acid  (glacial),  . 2 grams. 

Distilled  water  up  to  100  „ 


. 5 grains. 


. 5 

. 10 
. 1 oz. 


J5 


Mr.  Charles  W.  Gamble  has  pointed  out  an 
interesting  point  in  connection  with  intensification 
of  half-tone  negatives  by  lead.  If  the  mixture  of 
lead  and  silver  ferrocyanides  is  treated  with  fresh 
ammonium  sulphide,  the  dots  in  the  negative  come 
out  sharp  and  black,  but  if  the  ammonium  sulphide 
has  been  made  up  several  days,  each  dot  is  sur- 
rounded by  a grey  margin  instead  of  being  sharp. 
The  explanation  of  this  is,  that  on  exposure  to  the 
air,  ammonium  sulphide  is  oxidized  to  a mixture  of 
thiosulphate  and  polysulphides  which  have  a solvent 
action  on  the  silver,  which  is  first  dissolved  and 
then  re-precipitated  as  a blurred  margin  round  the 
dot. 


88 


PHOTO-SALTS 


CHAP TEE  VTI 
Feinting  in  Silver. 

From  the  short  account  given  on  p.  36,  the  reader 
will  have  learnt  something  about  the  photo-chlorides 
of  silver,  which  Carey  Lea  did  so  much  to  investigate. 
These  intermediate  compounds  between  ordinary 
silver  chloride  and  metallic  silver  are  of  most  varied 
colours,  ranging  from  white  through  shades  of  red 
and  purple  to  black.  They  are  permanent  in  the 
dark,  hut  are  altered  by  light.  Besides  these 
coloured  photo-chlorides  and  other  photo-salts  of 
silver  there  are  several  coloured  varieties  of  metallic 
silver,  which  in  this  state  more  resembles  a colloid 
substance  (see  p.  113),  and  possesses  the  remarkable 
property  of  dissolving  in  water.  In  addition  to  the 
ordinary  white  form  of  metallic  silver,  there  seem  to 
be  at  least  four  other  modifications.  The  first, 
which  we  may  call  A,  is  soluble,  forming  a deep  red 
solution  in  water.  When  concentrated,  or  if  nitrate 
of  ammonium  is  added  to  the  solution,  it  forms  a 
precipitate,  which  may  be  either  matt  black,  blue  or 
green,  whilst  moist.  As  soon  as  it  is  dry,  however, 


SOLUBLE  SILVEK. 


89 


it  acquires  a brilliant  metallic  surface,  having  a 
bluish-green  tint.  Modification  B is  insoluble,  and 
is  produced  from  the  foregoing  ; it  is  dark  reddish- 
brown  when  moist,  but  resembles  A when  dry. 
The  third  form,  C,  is  of  a dark  bronze  hue  when 
moist,  but  like  burnished  gold  when  dry.  No 
soluble  modification  of  this  exists,  but  a copper- 
coloured  variety  is  formed  under  certain  conditions. 
All  the  varieties  have  the  remarkable  property  of 
drying  with  their  particles  in  optical  contact,  pro- 
ducing perfect  mirrors  if  spread  out  on  paper  and 
allowed  to  dry.  Unfortunately,  like  the  photo- 
chlorides, these  forms  of  metallic  silver  are  affected 
by  light ; A and  B become  brown  after  some  hours, 
and  the  coppery  modification  of  C becomes  bright 
yellow.  In  spite  of  this,  several  occasions  can  be 
imagined  on  which  they  would  be  serviceable  for 
making  a large  mirror  for  immediate  use  in  the 
studio,  or  where  a large  reflecting  surface  is  required. 
C has  the  property  of  changing  into  ordinary  silver 
of  great  beauty  in  presence  of  moisture,  and  immedi- 
ately on  being  subjected  to  friction  in  any  part,  the 
action  spreading  to  the  rest  of  the  film.  The  reader 
has  probably  seen  a good  many  of  these  photo- 
chlorides and  varieties  of  metallic  silver  in  the 
ordinary  silver  printing  papers  after  exposure  behind 
the  negative. 

The  old  process  of  sensitizing  albumen  paper 
with  silver  nitrate  is  still  the  most  largely  used  of 
any  printing  process  in  spite  of  numerous  drawbacks. 


90 


ALBUMENIZED  PAPER. 


In  preparing  the  paper  on  a large  scale,  the  eggs 
are  broken  separately,  the  whites  separated  from  the 
yolks  and  run  into  drums.  This  albumen  is  then 
run  into  churns  driven  by  steam,  and  “ frothed,” 
being  allowed  to  stand  until  quite  limpid,  when 
it  is  decanted  off  from  the  embryos  and  stringy 
portions  of  the  white  of  egg  and  run  into  tall  glass 
jars  to  ferment.  After  this  it  is  filtered  and  again 
treated  to  the  frothing  process  and  allowed  to  settle, 
the  stringy  portions  being  now  finally  removed. 
Ammonium  chloride  is  added  to  the  albumen,  and 
Eives  or  Saxe  paper  is  coated  by  fioating  the  sheets 
on  the  surface  of  the  liquid.  The  paper  is  hung  up 
to  drain,  stored  for  some  time  and  re-albumenized, 
being  hung  up  to  drain  the  reverse  way.  This  pro- 
cedure equalizes  the  quantity  of  albumen  on  the 
surface. 

From  this  description  of  work  on  the  large  scale, 
the  reader  will  see  how  to  proceed  in  the  small  way 
if  ever  he  finds  it  necessary  to  do  so,  the*  following 
quantities  of  materials  being  used,  and  a whisk 
being  employed  instead  of  a churn: — 


Albumen,  . 
Ammonium  chloride, 
Eectified  spirit,  . 
Distilled  water,  . 


6 ozs. 

. 60  grams. 

. 96  minims. 

If  ozs. 


The  paper  is  sensitized  just  before  use  by  fioating 
on  a solution  of  silver  nitrate  containing  50  grs.  to 
the  oz.,  or  10  grams  in  100  c.c. 


PRINTING  AND  WASHING. 


91 


The  action  of  the  sensitizing  bath  is  to  convert 
the  silver  nitrate  into  chloride,  which  is  entangled 
in  the  albumen  by  interaction  with  the  ammonium 
chloride.  Besides  this,  however,  the  silver  nitrate 
has  an  important  action  on  the  albumen,  forming 
an  albumenate  of  silver,  which  is  insoluble  in 
water,  so  that  the  albumen  does  not  dissolve  off 
the  paper.  Consequently,  the  stronger  the  sensi- 
tizing bath  the  longer  will  the  paper  have  to  be 
floated,  as  the  silver  nitrate  penetrates  more  slowly 
through  the  insoluble  albumenate. 

In  printing  on  this  paper  the  action  is  probably 
very  complicated  as  the  albumenate  of  silver  takes 
part  in  the  reduction  as  well  as  the  chloride.  The 
ready  sensitized  paper,  used  so  largely  by  amateurs, 
contains  citric  acid  in  addition  to  the  other  con- 
stituents, which  still  further  complicates  matters. 

When  printed,  the  paper  is  washed  in  water  con- 
taining one  part  of  common  salt  in  40,  and  toned 
with  gold  or  other  more  or  less  permanent  reducible 
metal,  in  order  to  counteract  the  objectionable  red 
tones  of  the  silver  print.  In  washing  the  print 
before  toning,  the  reason  that  the  water  turns  milky 
is  that  the  soluble  silver  salts  react  with  the  salt  in 
the  water  to  form  chloride. 

Of  the  numerous  toning  baths,  the  acetate  is  that 
most  usually  employed.  The  gold  chloride  generally 
purchased  is  a double  chloride  of  gold  and  sodium 
and  is  frequently  acid.  It  is  important,  therefore, 
to  neutralize  the  gold  chloride  solution  by  shaking 


92 


TONING  WITH  GOLD. 


it  up  with  a little  powdered  chalk.  For  use  it  is 
convenient  to  dissolve  the  contents  of  the  15  grain 
tube  in  IJ  ounces  of  water,  making  approximately 
1 grain  to  1 dram  or  a 2 per  cent,  solution  ; or  if 
dissolved  in  50  c.c.  of  water,  a practically  2 per  cent, 
solution  of  the  commercial  salt,  or  a 1 per  cent, 
solution  of  gold  is  obtained.  The  following  Table 
shows  a few  of  the  various  formulae  recommended  by 
different  workers  for  toning  sensitized  paper  with 
gold. 

TABLE  VIII.— Gold  Toning  Baths. 


Each  to  be  made  up  to  10  ounces  with  water. 


Substances. 

I. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

Gold  chloride  (commer- 

2 

2 

2 

2 

1 

1 

2 

cial),  2%  solution,  . 

drams 

drams 

drams 

drams 

dram 

dram 

drams 

Acetate  of  soda,  . 

90 

grains 

48 

grains 

Borax,  .... 

96 

grains 

Bicarbonate  of  soda, 

4 

grains 

30 

grains 

Carbonate  ,, 

(washing  soda), 

10 

grains 

— 

Phosphate  of  soda. 

20 

grains 

Tungstate  of  soda, 

— 

40 

grains 

When  toning  has  reached  a stage  where  the  blue 
of  the  gold  neutralizes  the  objectionable  red  and 
orange  tones  of  the  original,  the  print  is  fixed  in  a 
10  per  cent.  (2  oz.  to  the  pint)  solution  of  sodium 
thiosulphate.  It  is  even  more  important  with 
prints  than  with  negatives  to  always  keep  the  fixing 
bath  in  perfect  condition.  The  least  trace  of  acid 


CHEMISTRY  OF  TONING. 


93 


means  the  presence  of  free  sulphur  (see  p.  77),  and 
free  sulphur  turns  the  whites  of  the  print  yellow. 
For  this  reason  combined  toning  and  fixing  baths 
cannot  be  too  strongly  condemned.  Consequently, 
the  fixing  bath  should  be  made  alkaline  by  the 
addition  of  ammonia,  or,  better,  bicarbonate  of  soda 
in  the  proportion  of  5 grains  to  each  ounce  of 
“ hypo.”  Always  test  with  litmus  paper  before  use  ; 
if  acid,  i.e.,  if  the  litmus  paper  turns  red,  add  more 
bicarbonate.  Toning  baths  should  be  made  alkaline 
with  bicarbonate  in  the  same  way,  if  on  the  acid 
side,  as  it  is  essential  that  the  bath  be  alkaline. 
After  toning  it  is  well  to  immerse  the  prints  in  salt 
and  water  before  fixing.  They  may  be  left  here 
until  all  the  batch  has  been  toned,  so  as  to  avoid 
contamination  of  the  fingers  with  the  fixing  bath 
whilst  toning  is  in  progress. 

The  chemistry  of  the  toning  process  is  as  follows  : 
In  the  alkaline  solution  the  gold  chloride  is  reduced 
first  of  all  from  auric  chloride  (Au  CI3)  to  aurous 
chloride  (Au  Cl)  ; then  an  atom  of  gold  is  deposited, 
an  atom  of  silver  taking  its  place,  thus, 

Aurous  chloride.  Silver.  Silver  chloride.  Gold. 

AuCl  4-  Ag  = AgCl  + Au. 

From  this  it  is  clear  that  other  metals  can  be 
used  for  toning  instead  of  gold.  With  a platinum 
toning  bath,  for  instance,  platinum  is  deposited  in 
the  place  of  the  silver,  and  with  a lead  toning  bath, 
lead  is  exchanged  for  the  silver  in  the  print.  The 


94 


GELATINO-CHLORIDE  PAPER. 


following  platinum  toning  bath  is  recommended  by 
Liesegang : — 

Potassium  chloroplatinite,  . *1  gram,  | grain. 

Nitric  acid,  . . . ”5  c.c.,  . 2 minims. 

Water,  ....  100  „ . 1 oz. 

Gelatino-chloride  and  collodio-chloride  papers  are 
emulsions  of  silver  chloride  and  an  organic  salt  with 
gelatin  in  the  one  case  and  with  collodion  in  the 
other.  These  papers  are  generally  known  as 
printing-out  ” papers. 

W.  K.  Burton’s  formula  for  gelatino-chloride 
emulsions  is  as  follows  : — 


A.  Ammonium  chloride. 
Gelatin,  . 

Distilled  Water, 

Soak  the  gelatin  and 
water  for  an  hour  and 
then  add 

Silver  nitrate,  . 
Distilled  water, 

B.  Sodium  citrate. 
Gelatin,  . 

Distilled  water. 

Allow  to  soak  for  an 
water-bath ; then  add 

Silver  nitrate,  . 

Citric  acid, 

Distilled  water. 


3*5  grams,  . 53  grains. 

27  „ . 420  „ 

850  C.C.,  . 30  ozs. 

ammonium  chloride  in  the 
dissolve  on  a water-bath ; 


9*7  grams,  . 150  grains. 

14  C.C.,  . J oz. 

2 grams,  . 30  grains. 

6*3  „ . 100 

100  C.C.,  . 3J  ozs. 

hour  and  dissolve  in  the 


3 grams,  . 45  grains. 

5 „ .80 

14  C.C.,  . J oz. 


COLLODIO-CHLORIDE  PAPER. 


95 


Mix  A and  B ; wash  as  directed  in  dry-plate 
emulsions,  and  after  keeping  for  three  or  four  days, 
coat  the  paper  by  floating. 

Geldmacher’s  formula  for  collodio-chloride  emul- 
sion is  as  follows : — 


A.  Pyroxylin,  . 

22*75  grams. 

6J  drams. 

Ether  (not  methylated), 

425  C.C., 

15  ozs. 

Alcohol  (not  methylated),  425  „ 

15  „ 

Castor  oil,  . 

3-5  „ . 

1 dram. 

B.  Silver  nitrate. 

20  grams. 

308  grains. 

Distilled  water,  . 

21*5  c.c., 

6 drams. 

Alcohol  (not  methylated),  42*5  „ 

IJ  ozs. 

C.  Citric  acid,  . 

5 grams, 

7 5 grains. 

Alcohol, 

70  C.C., 

2J  ozs. 

D.  Strontium  chloride, 

5 grams. 

7 5 grains. 

Alcohol, 

70  C.C., 

2 J ozs. 

Mix  C and  D and  add 

to  A,  shaking 

vigorously. 

In  the  dark  room,  add  B to  the  mixture  in  small 
portions  at  a time,  shaking  constantly.  The  emul- 
sion is  ready  for  use  after  standing  for  an  hour. 

Alpha  paper  is  essentially  a gelatin  emulsion 
of  silver  citrate.  The  following  is  Wellington’s 
formula  : — 


A.  Silver  nitrate,  . 
Citric  acid. 
Distilled  water,  . 


53*5  grams, 
53-5  „ 

142  C.C., 


825  grains. 


825 


5 ozs. 


B.  Sodium  chloride,  10 '7  grams. 
Potassium  bromide,  21*4  ,, 

Citric  acid,  . 53*5  „ 

Gelatin,  . . 21*4  „ 

Distilled  water,  142  c.c.. 


165  grains. 


330 

825 

330 

5 


3) 


33 

OZS. 


96 


TONING  PKINTING-OUT  PAPERS. 


Both  solutions  are  to  be  heated  to  66°  C.  A is 
then  added  to  B,  and  1600  grains  (10 4 grms.)  of 
gelatin,  previously  swollen  and  melted,  is  added  to 
the  mixture,  which  is  run  into  a dish  and  allowed 
to  set.  It  is  then  broken  up,  washed  and  re-melted 
before  coating  the  paper,  which  is  best  developed 
with  the  hydroquinone  formula  given  below  (p.  95) 
and  toned. 

As  regards  toning,  the  collodio-  and  gelatino- 
chloride  papers  may  be  treated  alike.  The  same 
baths  may  be  used  as  for  ordinary  sensitized  paper, 
but  these  papers  work  better  in  a bath  composed  of 
ammonium  sulphocyanide  and  gold  chloride  than 
in  any  other.  The  quantity  of  sulphocyanide  may 
vary  considerably,  but  as  it  has  a tendency  to  dis- 
solve gelatin,  it  is  not  advisable  to  use  more  than 
is  recommended  in  the  formula.  These  printing- 
out  papers  require  to  be  toned  somewhat  more  deeply 
than  ordinary  sensitized  paper.  The  gelatin  paper 
should  not  be  touched  with  the  fingers  as  the  gelatin 
is  apt  to  soften  with  the  warmth,  and  retain  the 
marks ; for  the  same  reason,  all  solutions  should  be 
kept  cold.  To  prevent  uneven  toning,  it  is  well  to 
give  the  prints  a thorough  washing,  preferably  in 
salt  and  water  (see  p.  87),  before  toning.  The 
following  bath  can  be  recommended : — 

Gold  chloride  (2%  solution),  . 6 c.c.,  1 dram. 

Ammonium  sulphocyanide  (10% 

solution),  . . . . 30  ,,  5 drams. 

Water,  .....  100  ,,  16  ozs. 


TONING  AND  FIXING  BATHS. 


97 


Ammonium  sulphocyanide  is  very  deliquescent, 
and  should  be  dissolved  in  water  at  once  to  form  a 
10%  solution.  In  making  up  the  bath,  always  mix 
the  sulphocyanide  with  the  water  first,  and  then  add 
the  solution  of  gold  chloride. 

In  toning,  it  should  always  be  borne  in  mind  that 
the  number  of  prints  that  can  be  toned  with  a given 
quantity  of  gold  depends  quite  as  much  upon  the 
nature  of  the  prints  as  upon  their  size.  A dark 
print  with  heavy  shadows  may  require  three  or  four 
times  as  much  gold  as  a light  print  of,  say,  a cloud 
effect.  It  is  important  when  economy  of  gold  is 
desired,  to  trim  the  prints  before  toning. 

The  following  formula  has  been  strongly  recom- 
mended by  printers : — 

Gold  chloride  (2%  solution),  1*5  c.c.,  . 3 drams.__ 

Ammonium  sulphocyanide 

(10%  solution),  . . 20  ,,  .2  ozs. 

Sodium  thiosulphate,  . 1 gram,  . 5 grains. 

Water  up  to  . . . 100  c.c.,  . 10  ozs. 

Numerous  other  formula3  are  in  existence  and 
will  be  found  in  the  various  year  books  and  other 
books  of  reference,  but  exigencies  of  space  forbid 
their  inclusion  here. 

Some  photographers  use  and  recommend  the 
combined  toning  and  fixing  baths.  These  may  be 
all  very  well  for  routine  work  in  careful  and 
experienced  hands,  but  they  are  wrong  in  principle 
and  the  least  carelessness  may  produce  disaster. 
The  author  never  uses  them  himself,  and  gives  the 

G 


98 


PRINTlNG-OUT  PAPERS. 


following  formulae,  which  is  due  to  Dr  Liesegang, 
under  protest,  so  to  speak : — 

Ammonium  sulphocyanide 

(10%  solution),  . . 10  C.C.,  10  drams. 


Distilled  water  up  to  . 100  c.c.,  12  „ 

To  60  parts  of  this  solution,  add  7 parts  of  a 2^ 
solution  of  gold  chloride,  diluted  with  an  equal  bulk 
of  water.  When  the  mixture  has  been  made,  add 
40  parts  of  old,  used,  combined  bath. 

Printing-out  papers  can  be  developed  after  a 
short  exposure,  and  can  then  be  toned  and  fixed  in 
the  usual  way.  Only  a faint  image  is  required  to 
start  with,  and  it  is  advisable  not  to  print  beyond  the 
point  where  the  details  just  begin  to  show  in  the 
half-tones.  It  is  well  to  follow  the  excellent  sug- 
gestion of  Mr  Wilson  of  the  Paget  Prize  Plate  Co. 
and  immerse  the  prints  in  a 10%  solution  of  potas- 
sium bromide  before  developing,  thus  changing  the 
silver  chloride  into  silver  bromide.  After  soaking 
in  this  solution  for  from  10  to  20  minutes,  passing  a 
clean  camel-hair  brush  over  the  surface  of  the  paper 
to  ensure  the  absence  of  bubbles,  the  paper  should 
be  thoroughly  washed  for  about  ten  minutes  in  run- 
ning water  to  remove  excess  of  potassium  bromide, 
which  would  render  the  development  too  slow. 
Then  develop  with  the  following: — 


Common  salt, . 

Alum,  .... 
Sodium  thiosulphate  (hypo). 


4 grams,  240  grains. 
2 „ 120  „ 

15  „ 2 ozs. 


BROMIDE  PAPER. 


99 


A.  Hydroquinone,  . 2 grams,  . 10  grains. 

Sodium  sulphite,  . 2 „ .10  „ 

Sulphurous  acid,  . 1 c.c.,  . 5 minims. 

Water  up  to  . . 100  „ . 1 oz. 

B.  Sodium  carbonate 

(washing  soda),  . 5 grams,  . oz. 

Water  up  to  . . lUO  c.c.,  . 10  ozs. 

For  use,  take  one  part  each  of  A and  B,  and  one 
part  of  water. 

The  papers  can  be  toned  with  platinum  ; for 
formula  see  p.  94. 

Bromide  paper  is  coated  with  a gelatino-broniide 
of  silver  emulsion  similar  to  that  used  for  dry 
plates,  but  generally  much  less  rapid.  The  follow- 
ing is  Dr.  Eder’s  formula  for  an  emulsion  suitable 
for  coating  paper : — 

A.  Ammonium  bromide,  . . 20  parts. 

Gelatin,  ....  50-80  „ 

Distilled  water,  . . . 400  „ 

Soak  the  gelatin  in  the  water  for  12  hours,  then 
dissolve  in  the  water-bath  at  50-60°  C.,  and  add 
the  bromide.  Take  the  emulsion  into  the  dark 
room  and  add,  with  constant  shaking, 

Silver  nitrate,  . . . .30  parts. 

Distilled  water,  ....  400  ,, 

After  standing  for  about  an  hour,  pour  out  into  a 
dish  to  set,  squeeze  through  muslin,  and  wash  in  the 
manner  described  on  page  52.  The  above  formula 
gives  black  tones.  If  brown  tones  are  required, 


100 


BROMIDE  PAPER. 


replace  two  parts  of  the  ammonium  bromide  by  two 
parts  of  potassium  iodide. 

Bromide  paper  may  be  developed  with  ferrous 
oxalate  or  with  most  of  the  dry  plate  developers, 
except  pyrogallic  acid.  The  author  much  prefers 
ferrous  oxalate.  The  following  is  a good  formula : — 

A.  Neutral  oxalate  of  potash,  23  grams,  1 lb.  avoir. 

Distilled  or  boiled  water,  100  c.c.,  3J  pints. 

B.  Ferrous  sulphate,  . .30  grams,  1 lb.  avoir. 

Sulphuric  acid,  . . *5  c.c.,  15  minims. 

Distilled  or  boiled  water,  100  „ 54  ozs. 

For  use,  add  one  part  of  B to  six  parts  of  A,  not 
the  reverse,  or  a precipitate  of  ferrous  oxalate  would 
be  formed.  A few  drops  of  10%  potassium  bromide 
solution  may  be  added  as  a restrainer. 

If  after  development  the  prints  were  to  be  put 
direct  into  water,  a precipitate  would  be  formed  in 
the  paper  of  ferric  hydrate.  To  avoid  this,  the  paper 
is  placed  in  dilute  sulphuric  acid  (say  oz.  in  a pint, 
or  25  c.c.  in  1000  c.c.),  which  dissolves  out  any  iron 
from  the  paper. 

As  regards  development  with  agents  other  than 
ferrous  oxalate,  the  combinations  that  can  be  made 
are  almost  unlimited.  For  practical  purposes,  any 
of  the  formulae  used  for  dry  plate  development  may 
be  employed,  but  the  strength  must  be  only  one- 
third  of  that  given  in  the  formulae  for  dry  plates. 
The  proportion  of  sulphite  in  each  ounce  or  100  c.c. 
of  developer,  however,  may  remain  the  same  or  be 


TONING  BROMIDE  PRINTS. 


101 


only  slightly  reduced,  so  as  to  ensure  absence  of 
stain. 

Bromide  prints  are  frequently  toned  with  platinum 
or  uranium  salts.  In  the  former  case,  the  platinum 
replaces  the  silver  to  a greater  or  less  extent. 
Uranium,  although  it  changes  the  tone  to  a reddish- 
brown,  acts  principally  as  an  intensifier,  and  can  be 
applied  beneficially  to  weak  prints.  It  is  important 
that  every  trace  of  “ hypo  ” be  removed  by  thorough 
soaking,  otherwise  toning  will  be  uneven.  Selle’s 
formula  for  uranium  toning  is  essentially  as  follows : 

Uranium  nitrate,  . . '5  gram,  grains. 

Potassium  ferricyanide,  . *5  „ ,, 

Acetic  acid  (glacial),  . dO  grams,  | dram. 

Water  up  to  . . 100  c.c.,  1 oz. 

After  toning,  the  print  should  be  washed  in  dilute 
acetic  acid  (say  1 to  30),  for  twenty  minutes  or 
longer. 


102 


BLUE  PRINTS. 


CHAPTEE  VIII. 

Printing  in  Salts  of  Iron. 

PRACTICALLY  the  whole  of  the  processes  for  printing 
in  salts  of  iron  depend  upon  the  fact  that  ferric 
salts  are  reduced  to  the  ferrous  state  by  the  action 
of  light,  ferric  oxalate,  Fe%  (C^2^4)3>  becoming  ferrous 
oxalate,  Ee"C204.  Potassium  ferricyanide  converts 
the  reduced  salt  into  insoluble  Prussian  blue,  the 
unreduced  ferric  salt  being  nearly  colourless  and 
soluble.  If  /errocyanide  of  potassium  be  used  as  a 
developer  instead  of  /errmyanide,  the  reduced 
portions  remain  colourless,  whilst  the  unreduced 
parts  are  turned  blue. 

The  paper  usually  employed  for  reproducing 
engineering  plans  and  for  making  blue  prints  from 
negatives,  is  coated  with  a mixture  of  ammonio- 
ferrous  citrate,  better  known  as  ammonio-citrate  or 
citrate  of  iron,  potassium  ferricyanide  and  gum 
arabic  in  water.  The  process  was  first  employed  by 


PRINTING  IN  IRON  SALTS. 


103 


Sir  John  Herschell  in  1842.  The  following  is 
Eock wood’s  formula  : — 

A.  Potassium  ferricyanide,  . 10  grams,  . 1 oz. 

Water,  ....  100  c.c.,  . 10  ozs 

B.  Ammonio-citrate  of  iron,  . 30  grams,  . 3 ozs. 

Gum  arabic,  . . . 5 ,,  . J oz. 

Water,  ....  100  c.c.,  . 10  ozs. 

Equal  parts  of  A and  B to  be  taken,  and  after 
standing  for  a few  minutes  until  quite  clear,  the 
paper  should  be  coated  by  means  of  a stiff  brush. 
The  paper  should  be  dried  quickly  and  kept  dry. 
It  is  fixed  by  washing  in  water  until  the  whites  are 
quite  clear.  If  over-printed,  a little  carbonate  of 
soda  may  be  added  to  the  water.  If  under-printed, 
fuller  density  may  be  obtained  by  adding  a little 
ferric  salt  to  the  first  wash  water  and  allowing  it  to 
remain  until  sufficient  depth  is  obtained.  This  is 
the  same  principle  as  re-developing  a gelatino- 
bromide  plate.  Spots  can  be  bleached  by  a weak 
solution  of  potassium  oxalate. 

This  paper  can  be  toned  with  various  substances. 
Strong  tea  containing  a little  sodium  carbonate 
changes  the  blue  to  black,  the  iron  forming  an  ink 
with  the  tannin.  The  colour  can  be  altered  by 
different  reagents,  sulphocyanide  turning  it  red,  and 
so  on. 

If  the  paper  be  coated  with  the  iron  solution  (B) 
only,  without  the  ferricyanide,  it  can  be  developed 
with  this  solution,  or  with  gold  chloride. 

The  process  of  making  a paper  for  subsequent 


104 


DEVELOPING  BLUE  PRINTS. 


development  with  ferrocyanide  of  potassium,  whereby 
the  whites  of  the  negative  come  out  white,  is  as 
follows,  using  Pizzighelli’s  formula : — 

A.  Gum  arabic,  . . .20  grams,  . 2 ozs. 

Water,  ....  100  c.c.,  . 10  „ 

B.  Ammonio-citrate  of  iron,  . 50  grams,  . 5 ,, 

Water,  ....  100  c.c.,  . 10  „ 

C.  Ferric  chloride,  . . 50  grams,  . 5 ,, 

Water,  ....  100  c.c.,  . 10  „ 

For  use,  add  20  parts  of  A to  8 parts  of  B,  and 
the  whole  to  5 parts  of  C.  Allow  to  stand  until 
clear  and  then  coat  the  paper.  As  the  reduced 
ferrous  is  lighter  than  the  ferric  salt,  the  image 
appears  lighter  than  the  back-ground. 

Develop  with : — 

Potassium  ferrocyanide,  . 20  grams,  . 2 ozs. 

Water,  ....  100  „ . 10  „ 

Paste  the  developer  on  the  surface  of  the  print 
with  a brush ; as  soon  as  dark  enough,  wash,  and 
fix  in  a 10%  solution  of  hydrochloric  acid  until  the 
whites  show  clear. 


PLATINUM  PRINTING. 


105 


CHAPTEE  IX. 

Printing  in  Platinum. 

Platinum  printing  is  not  a direct  process  ; it  is 
really  an  iron  printing  process,  but  instead  of  bring- 
ing out  the  reduced  ferrous  image  with  ferricyanide, 
a platinum  salt  is  used,  the  platinum  being  reduced 
by  the  ferrous  image  to  form  a permanent  print. 
The  platinum  salt  can  be  incorporated  in  the  sensi- 
tizing solution  that  is  applied  to  the  paper,  as  in  the 
cold  process,  or  the  iron  image  can  be  obtained  first 
by  printing  on  paper  coated  by  ferrous  oxalate  and 
treating  this  afterwards  with  a solution  containing 
platinum  as  in  the  hot -bath  process.  Platinic 
chloride  PtCl4  can  be  used,  but  the  effect  is  not 
good,  as  the  salt  has  to  be  reduced  such  a long  way, 
so  the  lower  or  platinous  chloride  gives  better 
results.  This  salt  is  nearly  insoluble  in  water, 
but  a double  chloride  of  platinum  and  potassium 
is  very  soluble,  so  that  the  latter  or  potassium 
chloroplatinite,  as  it  is  generally  called,  is  the  actual 
salt  employed. 

By  the  addition  of  mercuric  or  palladium  salts 


106 


PREPARING  THE  PAPER. 


to  the  sensitizing  solution,  “ sepia-”  toned  images 
can  be  secured.  The  sepia  tone  does  not  appear 
to  be  due  to  any  admixture  of  a mercury  or  pallad- 
ium compound,  but,  as  V.  Hubl  has  shown,  to  a 
peculiar  condition  of  the  platinum  itself. 

W.  Willis  and  Captain  Pizzighelli  are  the  two 
best  known  workers  on  platinum  printing,  the  hot- 
bath  process  of  the  former  inventor  being  still 
the  most  reliable  printing  method,  and  that  most 
generally  used.  Eives  paper,  No.  74,  is  sized  with 
arrowroot  and  gelatin,  in  some  such  proportion  as 
the  following  :* — 


Arrowroot,  . 
Nelson’s  gelatin,  . 
Alum, 

Water  up  to 


500  grains. 
180  „ 
no  „ 

120  ozs. 


The  gelatin  is  allowed  to  swell  and  then  dissolved 
at  about  80°  P. ; the  arrowroot,  being  made  into  a 
thin  cream  with  a little  of  the  cold  water,  is  then 
poured  in.  The  paper  is  sized  on  this  for  about 
three  minutes  by  floating,  and  after  being  hung  up 
to  dry  is  sensitized  by  coating  with  a solution  made 
of  iron  sensitizing  salts,  supplied  in  two  solutions, 
A and  B,  by  the  Platinotype  Co.,  and  chloroplatinite 
of  potassium,  as  follows  : — 

Iron  solution  A,  . . . .3  parts. 


Of  the  mixture  take  7 drams,  make  up  to  1 oz. 
* “E.  A.R.”  in  The  Photogram. 


DEVELOPING  PLATINUM  PRINTS. 


107 


with  distilled  water,  and  dissolve  in  it  48  grains 
chloroplatinite  of  potassium. 

Coat  the  paper  in  a room  heated  to  70°  F.,  the 
atmosphere  being  kept  moist.  The  paper  should 
be  allowed  to  get  surface  dry  and  should  then  be 
dried  completely  on  an  iron  plate  in  front  of  a fire, 
taking  care  not  to  overheat.  To  keep  the  paper 
dry,  it  should  be  stored  in  a tin  having  a lid  at 
at  each  end,  the  bottom  lid  containing  asbestos  fibre 
soaked  in  strong  calcium  chloride,  and  dried  bone  dry 
by  beating  on  an  iron  plate.  A perforated  zinc  grat- 
ing should  cover  the  calcium  chloride  and  asbestos  to 
prevent  any  contact  with  the  paper. 

It  is  important  to  keep  the  paper  as  dry  as 
possible  whilst  printing,  and  for  this  purpose  sheets  of 
india-rubber  are  placed  behind  the  paper  in  the 
printing  frames.  Printing  is  allowed  to  continue 
until  a faint  iron  image  is  visible,  when  it  is  de- 
veloped with  a solution  of  oxalate  of  potash  at  a 
temperature  not  lower  than  100°  F.  The  solution 
of  oxalate  of  potash  contains — 

Potassium  oxalate  (neutral),  , .16  parts. 

Water,  60  „ 

Hard  negatives  or  under-exposed  prints  require  a 
hotter  oxalate  bath,  as  it  tends  to  soften  and  flatten 
the  detail. 

When  developed  sufficiently,  the  prints  are  fixed 
without  washing  in  a bath  containing — 

Hydrochloric  acid,  . . . . 1 part. 

Water,  . . . . . .60  parts. 


108 


TONING  WITH  CATECHU. 


The  solution  is  poured  away  after  a few  minutes, 
and  fresh  poured  on,  this  being  again  repeated.  The 
object  is  to  dissolve  out  every  trace  of  iron  and 
unreduced  platinum  salt.  The  paper  must  be  washed 
to  remove  the  acid. 

Paper  is  made  for  developing  in  the  cold,  but  this 
paper  gives  very  brilliant  results  in  the  hot  bath. 

By  adding  mercuric  or  cupric  chloride  to  the  de- 
veloping solution  a sepia-tone  is  produced.  Various 
substances  can  be  used  to  tone  or  intensify  platinum 
prints,  but  with  the  exception  of  catechu,  they  are 
not  to  be  recommended.  Mr  J.  Packham  has  done 
much  to  introduce  toning  with  catechu,  and  M.  A. 
Villain  contributed  an  interesting  article  last  year 
to  The  Photogram  on  the  subject.  The  toning-bath 
is  prepared  by  boiling  7 grams  of  powdered  Bombay 
catechu  with  150  c.c.  of  water  for  ten  minutes,  cool- 
ing, adding  30  c.c.  of  alcohol,  and  filtering.  Of  this 
concentrated  solution  5 c.c.  are  taken  and  made  up 
to  500  c.c.  at  60°  F.  As  the  catechu-tannic  acid  in 
the  catechu  combines  to  form  an  inky  compound 
with  iron,  it  is  important  that  every  trace  of  the 
latter  be  removed  from  the  paper  before  toning. 


THE  CARBON  PROCESS. 


109 


CHAP  TEE  X. 

The  Bichromate  Printing  Processes, 

All  that  can  be  told  about  the  chemistry  of  the 
bichromate  processes,  so  far  as  it  is  known,  can  be 
said  in  a very  few  words,  the  subsequent  applica- 
tions of  this  knowledge  being  purely  mechanical 
There  are  two  chromates  of  potassium,  the  normal 
yellow  chromate  (K2Cr04),  and  the  acid  orange 
chromate  (K2Cr.207).  When  the  latter  is  mixed 
with  a colloid  organic  substance  (see  p.  113)  and 
exposed  to  light  under  a negative,  two  important 
changes  are  noticed  : the  organic  matter  is  rendered 
comparatively  insoluble  where  the  light  has  acted, 
and  the  material  has  lost  its  power  of  absorbing 
water  and  becoming  sticky,  or  “ tacky.”  On  these 
facts  the  whole  of  the  bichromate  processes  depend. 

In  the  carbon  process,  carbon,  Bartolozzi  red  or 
some  other  colouring  matter  is  incorporated  with 
gelatin,  and  made  into  thin  sheets  of  “ tissue,”  which, 
about  twelve  hours  before  use,  are  sensitized  by 
immersing  in  a 5 per  cent,  solution  of  potassium 
bichromate  for  three  minutes  in  winter  and  two  in 


110 


CARBON  TISSUE. 


summer,  at  60°  F.  It  is  then  hung  up  to  dry  in  the 
dark.  The  exposure  is  made  under  a negative,  the 
time  required  being  judged  by  means  of  an  actino- 
meter.  After  exposure,  the  tissue  is  transferred 
from  its  own  paper  to  another  paper  prepared 
specially  beforehand  by  coating  with 

Nelson’s  No.  1 gelatin,  . . . J oz. 

Water,  ......  10  ozs. 

Allow  the  gelatin  to  soak  for  an  hour  in  the 
cold  water,  and  then  dissolve  in  a water -bath. 
When  dissolved,  stir  in  half  a dram  of  formalin. 
Brush  well  over  the  surface  of  the  paper,  and  allow 
to  dry.  The  object  of  this  is  to  make  sure  that  the 
tissue  will  stick  fast  when  squeegeed  on  to  the 
paper. 

The  transfer  paper  is  soaked  in  water  for  a time, 
which  varies  according  to  the  thickness  of  the 
paper.  The  tissue  is  then  placed  in  the  same  water 
with  the  prepared  paper,  and  when  the  tissue 
begins  to  flatten,  the  two  are  lifted  from  the  water 
together,  being  then  squeegeed  into  close  contact  by 
means  of  a flat  squeegee.  After  being  pressed  be- 
tween blotting  boards,  the  whole  is  immersed  in 
hot  water  at  about  110°  F.  As  soon  as  the  gelatin 
begins  to  soften  round  the  edges,  the  original  sup- 
porting paper  is  removed. 

The  back  of  the  sensitive  gelatin  film  is  now 
uppermost,  the  surface  on  which  the  light  has 
fallen  being  beneath.  Where  the  light  has  acted 


SINGLE  AND  DOUBLE  TRANSFER. 


Ill 


strongly  the  gelatin  is  insoluble  nearly  right  through, 
but  in  the  parts  corresponding  to  the  black  parts  of 
the  negative  only  a thin  film  is  insoluble.  By 
washing  the  film  from  the  back,  which  is  now 
uppermost,  the  soluble  portions  will  be  washed 
away,  leaving  a sort  of  raised  map,  the  hills  corre- 
sponding to  the  light  parts  of  the  negative,  and  the 
dales  to  the  dark  portions.  Where  the  gelatin  be- 
comes insoluble  it  entangles  and  fixes  the  colouring 
matter,  so  that  a print  in  monochrome  with  all  the 
gradations  of  the  original  is  produced. 

The  method  just  described  is  that  of  single  trans- 
fer, the  right  and  left  of  the  original  subject  being 
reversed.  In  some  cases  this  is  objectionable,  so 
the  tissue  is  developed  on  a temporary  support,  con- 
sisting generally  of  opal  glass,  coated  with  the  fol- 
lowing : — 

Pure  bee’s-wax,  . . . . 2 drams 

Yellow  resin,  . . . . . 6 „ 

Turpentine,  . . . . .1  pint 

any  excess  being  removed  by  polishing  with  a 
cloth.  Paper  coated  with  a film  of  partially  soluble 
gelatin,  to  be  used  as  a final  support.  Before  use, 
a sheet  is  soaked  for  half-an-hour  in  a 2 per  cent, 
solution  of  alum,  and  then  placed  in  water  with  the 
supported  tissue,  which  should  be  transferred  in  the 
manner  described  under  single  transfer. 

In  both  cases  the  development  should  be  carried 
out  with  warm  water,  the  temperature  of  which 


112, 


ARTIGUE  PAPER. 


can  be  varied  according  to  the  correctness  of  the 
exposure,  higher  temperature  being  employed  for 
under-exposed  prints.  After  development,  they 
should  receive  a final  wash  with  cold  water,  and 
should  then  be  soaked  in  a 5 per  cent,  solution  of 
alum  until  all  bichromate  stain  has  been  removed, 
when  a final  rinse  with  cold  water  is  given.  The 
development  vshould  be  carried  out  as  soon  as  pos- 
sible after  printing,  as  the  action  once  started  by  the 
light  continues  automatically  in  the  dark.  It  is 
advisable  to  “ safe  edge  ” the  print  before  exposing 
by  protecting  the  margin  of  the  negative  from  the 
light  by  means  of  black  paper.  All  who  are  inter- 
ested in  carbon  printing  should  read  J.  A.  Sinclair’s 
excellent  monograph,  from  which  the  above  formulae 
have  been  taken.  It  appeared  together  with  other 
valuable  and  interesting  papers  on  the  bichromate 
processes  in  the  Journal  of  the  Royal  Photographic 
Society  for  May  1896,  the  set  of  papers  being  sub- 
sequently published  by  Dawbarn  & Ward,  Ltd. 

A very  beautiful  process  for  carbon  printing 
without  transfer  has  been  revived  recently,  and  is 
known  as  the  Artigue  or  bichromate  gum  process,  an 
account  of  which  will  be  found  in  Mr  Sinclair’s  paper. 
Instead  of  gelatin,  a warm  black  pigment  is  worked 
up  with  gum,  and  coated  on  paper.  This  is  sensi- 
tized in  a 2 per  cent,  solution  of  bichromate  of 
potash,  and  exposed  under  the  negative  without  a 
“ safe  edge,”  an  actinometer  being  employed  as  in 
the  ordinary  carbon  process.  In  development,  the 


HALF-TONE  AND  COLLOTYPE. 


113 


paper  is  first  treated  with  warm  water,  and  then 
with  a mixture  of  warm  water  and  fine  sawdust. 
After  development  is  complete  the  paper  is  soaked 
in  a 5 per  cent,  solution  of  alum,  and  then  washed 
in  cold  water. 

In  the  half-tone  process  of  reproducing  photo- 
grams and  tone  drawings,  a copper,  or  sometimes  a 
zinc,  plate  receives  a coating  of  gelatin  or  other 
colloid,  which  is  sensitized  with  bichromate.  This 
is  exposed  under  a negative  made  from  the  original 
through  a cross  line  or  other  screen  which  breaks 
up  the  tones  into  dots.  After  printing,  the  plate 
is  developed  by  washing,  and  etched  with  ferric 
chloride  or  an  acid.  There  are  various  modifica- 
tions of  this  process,  all  depending  on  the  action  of 
light  causing  the  gelatin  to  become  insoluble.  For 
details  of  these  processes  other  works  should  be 
consulted. 

In  collotype,  advantage  is  taken  of  the  fact,  pre- 
viously mentioned,  that  when  bichromatized  gelatin 
is  acted  upon  by  light  it  loses  its  tendency  to  absorb 
water,  and  becomes  tacky.  After  printing  under 
the  negative,  the  sheet  of  gelatin  is  fixed  on  the 
press,  and  kept  moist.  Where  the  light  has  acted, 
the  surface  takes  the  ink  in  proportion  to  the 
amount  of  light  that  has  fallen  upon  it.  Several 
other  processes  depend  upon  this  selective  action  of 
the  gelatin  as  regards  greasy  ink. 

Glue,  fish-glue,  size  and  isinglass  are  all  forms  of 
gelatin.  They  are  colloids,  i.e.,  they  will  absorb 

H 


114 


ASPHALTUM. 


water  to  an  indefinite  extent,  but  do  not  pass 
through  animal  membranes,  such  as  bladder,  as  a 
solution  of  salt,  sugar,  or  other  crystalloid  substances 
would  do.  For  photographic  purposes,  gelatin 
should  contain  little  ash — not  more  than  about  3 
per  cent. — should  take  up  from  five  to  ten  times  its 
weight  of  water  when  soaked  in  the  cold,  and  suf- 
ficient to  dissolve  it  on  warming  to  85°  F. 

In  the  common  line-engraving  process,  asphaltum 
is  generally  used  as  the  sensitive  substance.  This 
asphaltum  or  bitumen  is  obtained  from  deposits  of 
pitch  in  different  parts  of  the  world.  It  has  a pecu- 
liar smell,  and  resembles  the  heavier  portion  of  gas 
tar.  It  is  partly  soluble  in  alcohol  and  ether,  more 
so  in  benzene  and  essential  oils,  and  dissolves  com- 
pletely in  chloroform,  carbon  bisulphide,  and  mineral 
oils.  Caustic  alkalis  dissolve  it ; hot  sulphuric 
acid  dissolves  and  decomposes  it,  but  nitric  acid  is 
without  action  upon  it.  Asphaltum  is  sensitive  to 
light,  and  is  obtained  in  best  condition  by  exhausting 
with  ether,  the  insoluble  portion  being  dissolved  in 
benzene.  A plate  is  coated  with  a varnish  of  this 
material,  and  exposed  to  light  under  a negative  or 
transparency,  being  developed  with  a mixture  of 
benzene  and  turpentine,  which  dissolves  off  the 
bitumen  that  has  not  been  rendered  insoluble  by 
light.  The  plate  is  then  etched  and  treated  in 
various  ways. 


LIGHT  FILTERS. 


115 


CHAPTEK  XL 
Orthochromatism. 

Light  does  not  affect  an  ordinary  gelatino-bromide 
emulsion  in  the  same  manner  as  it  does  the  eye. 
The  latter  is  most  sensitive  to  the  yellow  of  the 
spectrum  in  the  neighbourhood  of  the  sodium  or  D 
line,  but  the  violet  and  ultra-violet  part  of  the 
spectrum  has  the  greatest  effect  on  a gelatino- 
bromide  film.  To  remedy  this  defect,  yellow  or 
yellow  orange  light-filters  are  introduced,  either  in 
front  of  the  lens,  or  between  the  lens  and  the 
plate.  The  effect  of  this  is  to  cut  off  the  violet 
end  of  the  spectrum  to  a greater  or  less  extent. 
The  author  has  investigated  a large  number  of  these 
filters,  and  has  found  considerable  variations  in  their 
absorptive  powers.  As  a general  rule,  the  gelatin 
or  collodion  filters  should  be  avoided,  as  the  colour- 
ing matter  in  this  form  has  a great  tendency  to 
fade.  The  filters  made  of  flashed  glass  are  the 
most  satisfactory.  The  question  of  what  filter  to 
employ  is  a very  difficult  one,  as  the  action  depends 
so  largely  on  the  strength  of  the  light.  It  is  un- 


116 


SENSITIZERS  FOR  DIFFERENT  RAYS. 


fortunate  that  no  standard  light-filters  have  yet  been 
fixed  upon  for  iso-chromatic  work. 

In  addition  to  this  means  of  modifying  the  light 
before  reaching  the  plate,  it  has  been  found  that 
certain  organic  dyes  have  an  important  influence 
on  the  absorptive  power  of  the  silver  salt  for 
the  different  parts  of  the  spectrum.  The  undyed 
gelatino-bromide  plate  is  most  affected  by  the 
blue  rays,  the  action  of  the  green  and  red  on  the 
plate  being  very  small  in  comparison.  In  a 
plate  dyed  with  ammoniacal  eosin,  the  action, 
although  still  greatest  in  the  blue  and  about  the 
same  in  the  violet,  extends  right  up  to  the  yellow 
green,  falling  away  rapidly,  however,  at  this  point. 
Ammoniacal  erythrosin  renders  the  action  com- 
paratively uniform  from  the  green-blue  to  the  end 
of  the  visible  violet.  In  the  green-blue  there  is  a 
rapid  falling-off,  as  is  the  case  with  eosin,  followed 
by  a rise  in  the  green,  the  maximum  action  being 
reached  in  the  yellow  instead  of  the  yellow-green 
as  with  eosin,  and  the  action  extends  with  lessen- 
ing effect  right  through  the  orange.  Ammoniacal 
rose  Bengal  gives  a very  similar  effect,  but  the 
maximum  is  in  the  yellow-orange  and  extends 
further  into  the  red.  Ammoniacal  cyanin  has  its 
maximum  effect  in  the  red. 

Speaking  generally,  rose  Bengal  is  the  best  sen- 
sitizer for  the  yellow  green,  and  cyanin  for  the  red. 
A solution  of  one  part  of  the  dye  in  ten  thousand 
of  water  is  a convenient  strength  to  use,  one  part 


COLOUR  SENSITIZERS. 


117 


of  ammonia  being  added  to  each  hundred  parts  of 
water  or  alcohol.  After  soaking  the  plates  for  two 
minutes  in  the  solution  of  the  dye,  they  are  washed 
to  remove  the  excess  of  dye,  and  dried  before 
exposure.  As  a rule,  orthochromatic  plates  lose 
their  sensitiveness  and  go  wrong  more  rapidly  than 
ordinary  plates,  and  should  be  used  as  soon  as 
possible  after  manufacture.  They  tend  also  to  fog 
if  forced  in  development.  These  drawbacks,  how- 
ever, are,  as  a rule,  insignificant  compared  with  the 
advantages  gained  in  colour  correctness,  and  it  is 
only  under  trying  conditions,  such  as  long  storage, 
that  these  defects  interfere  seriously  with  the  use  of 
the  plates.  The  brands  of  colour- sensitized  plates 
now  in  the  market  are  a great  improvement  on  the 
early  orthochromatic  plates,  and  possess  better 
keeping  properties. 

Coerulein,  alizarin  blue,  and  other  dyes  are  used 
as  sensitizers  for  the  red,  besides  those  mentioned. 


118 


CHEMICAL  PURITY. 


CHAPTEE  XII. 

IMPUPJTIES  AND  SUBSTANCES  THAT  ALTER  IN  THE  AIR. 

It  is  extremely  probable  that  no  substance  has  ever 
been  obtained  chemically  pure.  Xo  one  who  has  not 
occupied  himself  in  chemical  research  or  read  the 
memoirs  of  those  who  have  done  so  can  have  any  idea 
of  the  almost  insuperable  difficulties  to  be  encountered 
in  obtaining  a substance  in  a state  of  purity.  In  fact, 
the  word  “ pure  ” as  applied  to  chemicals  is  entirely 
comparative.  It  is  impossible  to  obtain  pure  water, 
for  instance,  in  glass  vessels  and  in  the  air,  as  the 
water  attacks  and  dissolves  out  the  alkali  from  the 
glass  on  the  one  hand  and  dissolves  air  on  the  other. 
Distillation  in  platinum  vessels  in  a vacuum  is  the 
only  method  of  obtaining  water  in  the  pure  state, 
and  then  the  purity  is  probably  far  from  abso- 
lute. Consequently,  “ pure  ” in  a chemical  dealer’s 
list  means  freedom  from  any  gross  impurity.  For 
many  purposes  the  “ commercial  ” variety  of  che- 
mical answers  quite  as  well  for  photographic  pur- 
poses as  the  pure,”  but  there  are  instances  in 
which  it  is  necessary  to  guard  against  some  par- 


IMPURITIES  IN  WATER. 


119 


ticular  impurity , and  these  cases  are  indicated 
below. 

Water,  as  ordinarily  supplied  from  the  tap  or  the 
weU,  is  a very  impure  material.  Apart  from  actual 
suspended  matter,  well  or  spring  water  contains 
varying  quantities  of  carbonate  and  sulphate  of  lime 
and  magnesia,  phosphates,  nitrates,  chlorides — 
generally  of  sodium — and  a certain  quantity  of 
ammonia.  Surface  water  usually  contains  more 
ammonia,  not  much  lime  and  magnesia,  but  a certain 
quantity  of  peaty  matter.  Eain  water  is  fairly  pure 
unless  the  roof  from  which  it  is  collected  is 
particularly  dirty.  Occasionally  a water  contains 
iron,  and  there  are  rarer  impurities  which  need  not 
be  considered  here.  The  worst  impurity  from  a 
photographic  point  of  view  is  chloride,  which  reacts 
with  silver  nitrate  to  form  insoluble  silver  chloride ; 
excess  of  lime  or  magnesia  is  often  objectionable, 
particularly  where  oxalates  are  used,  as  insoluble 
oxalates  of  lime  and  magnesia  are  formed  ; iron  is,  of 
course,  fatal,  but  does  not  often  occur ; peaty  matter 
is  objectionable  as  it  stains  printing  papers.  All 
these  impurities  may  be  removed  by  distilling  the 
water,  rejecting  the  first  pint  that  comes  over  as  it 
contains  nearly  all  the  ammonia.  Boiling  is  sufficient 
to  precipitate  the  carbonates  of  lime  and  magnesia, 
or  temporary  hardness,  but  the  sulphates,  or  per- 
manent hardness,  still  remain. 

Commercial  sulphuric  acid  contains  lead  and 
other  impurities.  Acid  of  good  quality  is  so  cheap 


120 


IMPURITIES  IN  ACIDS  AND  ALKALIS. 


that  it  should  be  used  for  all  photographic  purposes. 
It  should  not  be  exposed  to  the  air  as  it  absorbs 
water  rapidly,  and  in  diluting,  the  strong  acid  should 
always  be  added  to  the  water  instead  of  vice  versd, 
as  great  heat  is  developed. 

Commercial  hydrochloric  acid  or  muriatic  acid 
invariably  contains  iron.  Photographers  should 
avoid  an  acid  that  shows  any  trace  of  yellow. 

Alkalis,  whether  caustic  or  carbonate,  contain 
various  impurities.  It  is  well  to  filter  the  solutions, 
when  making  up  concentrated  developers,  etc., 
through  a plug  of  asbestos  or  glass  wool,  or  to  allow 
the  solution  to  stand  and  decant  off  the  clear  portion. 
Alkalis  act  strongly  on  the  glass  of  the  bottles  con- 
taining them,  and  a clear  solution  generally  has  a 
deposit  at  the  bottom  after  awhile.  Alkalis  should 
never  be  kept  in  stoppered  bottles,  as  the  stoppers 
become  hopelessly  fixed  after  a short  time. 

Cyanide  of  potassium  deteriorates  somewhat 
rapidly  owing  to  the  carbonic  acid  of  the  air  turning 
out  the  prussic  (hydrocyanic)  acid.  Old  cyanide 
should  never  be  used,  as  it  probably  contains 
nothing  but  carbonate.  See  that  the  cyanide  you 
buy  has  not  been  in  the  shop  for  a long  time ! 

Sulphocyanide  is  very  hygroscopic,  i.e.,  it  absorbs 
water  from  the  air.  For  this  reason  it  is  best  to 
convert  it  into,  say,  a 10°/^  solution  as  soon  as 
possible  after  purchasing. 

Sulphites  and  bisulphites  should  be  kept  in 
stoppered  or  well-corked  bottles,  which  should  not 


IMPURITIES  IN  IRON  SALTS. 


121 


have  a large  air  space  above  the  crystals,  as  the  air 
oxidizes  them  rapidly  to  sulphates,  in  which  condition 
they  are  useless  to  the  photographer. 

Thiosulphate  (“  hypo  ”)  as  usually  sold  is  pure 
enough  for  the  photographer’s  purposes.  When 
making  up  a solution  care  should  be  taken  to 
neutralize  any  acidity  with  a little  ammonia  or 
sodium  bicarbonate.  Thiosulphate  solutions  oxidize 
readily  in  the  air,  and  fixing  baths  become  acid  on 
keeping.  (See  also  page  73.) 

Ferrous  sulphate  contains  more  or  less  ferric  salt, 
due  to  oxidation,  and  any  crystals  that  show  a 
yellow  or  brownish  tinge  should  be  picked  out  and 
thrown  away.  Some  chemists  keep  pieces  of 
metallic  iron  at  the  bottom  of  their  solutions  of 
ferrous  sulphate,  but  a better  plan  is  to  fill  a number 
of  small  bottles  quite  full,  cork  them,  melt  up  some 
paraffin  candle  ends,  and  dip  the  tops  of  the  bottles 
into  the  paraffin  for  a few  moments.  In  this  con- 
dition the  contents  of  the  bottles  can  be  kept  from 
the  air  until  required.  If  the  ferrous  sulphate 
solution  be  put  into  a large  bottle,  air  is  admitted 
every  time  the  stopper  is  taken  out,  and  the  air 
space  above  the  solution  gets  larger  as  the  material 
is  used,  so  that  deterioration  goes  on  at  an 
increasingly  rapid  pace. 

Ferric  chloride  nearly  always  contains  free 
hydrochloric  acid  and  sometimes  ferrous  chloride, 
but  this  is  not  usual.  For  etching  purposes  the 
presence  of  free  hydrochloric  acid  is  an  advantage, 


122 


IMPURITIES  m SILVER  AND  GOLD. 


SO  long  as  there  is  not  too  much  of  it.  Neutral  or 
nearly  neutral  ferric  chloride  has  a tendency  to 
deposit  basic  salts,  Le.,  compounds  of  oxide  and 
chloride,  and  this  should  be  guarded  against.  If  too 
acid,  the  resist  may  come  away  from  the  plate  when 
etching.  Only  experience  can  tell  the  etcher  when 
his  bath  is  in  the  right  condition.  If  it  shows  a 
tendency  to  deposit,  a little  hydrochloric  acid  should 
be  added ; if  too  acid,  it  is  well  to  add  a little  ferric 
hydrate,  kept  for  the  purpose  and  made  by  adding 
ammonia  to  ferric  chloride  solution,  allowing  the  jelly 
to  settle  as  far  as  it  will,  decanting  off  the  clear 
portion,  adding  hot  water,  and  again  decanting. 

Silver  nitrate  is  generally  pure,  but  does  occasion- 
ally contain  copper,  which  can  be  detected  by  the 
colour  of  the  solution.  It  is  necessary  to  keep  all 
silver  salts  from  the  light,  as  they  darken  and  spoil. 

Gold  chloride,  as  obtained  commercially,  contains 
hydrochloric  acid,  which  requires  to  be  neutralized 
with  a little  chalk  or  whiting.  Instead  of  the  pure 
salt  the  double  chlorides  of  gold  with  sodium  or 
potassium  are  often  sold.  These  are  quite  as 
convenient  for  photographic  purposes  as  the  pure 
chloride,  and  so  long  as  the  photographer  gets  his 
proper  quantity  of  metallic  gold,  it  is  of  no  conse- 
quence whether  it  is  in  the  form  of  pure  chloride 
or  not. 


RECOVERING  SILVER. 


123 


CHAPTEE  XIII. 

Eecovery  of  Eesidues. 

The  waste  gold,  silver,  and  platinum  salts  contained 
in  used  up  fixing-  and  toning-baths,  spoilt  sensitized 
paper,  etc.,  are  often  saved  and  treated  for  the 
recovery  of  the  metals.  It  is  rarely  worth  the 
while  of  an  amateur  to  trouble  about  saving  his 
residues  unless  he  works  on  a very  large  scale,  but 
it  is  a matter  that  should  not  be  neglected  by  the 
professional  photographer.  The  fixing-baths,  satur- 
ated with  the  double  thiosulphate  of  silver  and 
sodium,  are  most  worth  attention.  Every  five 
ounces  of  “ hypo  ” is  capable  of  taking  up  about  two 
ounces  of  silver,  and  although  the  saturation  point  is 
never  reached  in  ordinary  practice,  yet  fixing-baths 
that  have  had  a large  number  of  plates  and  papers 
passed  through  them  do  contain  a considerable  pro- 
portion of  silver.  The  old  fixing-baths  are  thrown 
into  a tub  with  a solution  of  “ liver  of  sulphur  ” — 
a complicated  mixture  of  sulphides  and  other  things 
obtained  by  fusing  sulphur  with  potassium  carbonate 
— which  precipitates  the  silver  as  sulphide.  When 
the  tub  is  nearly  full,  a sample  should  be  taken  in 
a test-tube  or  small  vessel,  and  a few  drops  of  liver 
of  sulphur  solution  should  be  added  to  it.  If  no 


124 


SILVER  AND  GOLD  RESIDUES. 


precipitate  forms,  all  the  silver  has  been  deposited  ; 
if  the  liquid  turns  brown,  more  liver  of  sulphur  must 
be  added  to  the  tub.  When  the  deposit  has  quite 
settled,  the  clear  portion  of  the  liquid  should  be 
drawn  off  through  a tap  in  the  side  about  a foot 
from  the  bottom.  In  time  the  sludge  of  silver 
sulphide  will  reach  the  level  of  the  tap,  when 
the  cask  should  be  emptied  by  running  it  out 
through  a hole  at  the  bottom,  closed  in  the  ordinary 
way  by  a wooden  plug.  Underneath  the  hole  at 
the  bottom  of  the  cask,  a large  glass  funnel  con- 
taining a rag  or  filter  should  be  placed,  and  the 
sludge  should  be  run  on  to  this : the  liquid  portion 
filters  through,  leaving  the  solid  silver  sulphide  on 
the  filter.  It  should  be  allowed  to  dry  and  then 
labelled  “ silver  sulphide  ” and  sent  to  a refinery  to 
be  reduced. 

Scraps  of  sensitized  paper,  gelatino-chloride, 
bromide,  and  other  papers  should  be  burnt  to  an 
ash,  and  forwarded  to  the  refiner. 

Toning-baths  are  treated  with  solution  of  ferrous 
sulphate,  which  reduces  the  gold  to  the  metallic 
state. 

The  reduction  of  the  silver  is  performed  at  the 
refiner’s  by  fusing  the  sulphide,  etc.,  with  red  lead, 
etc. ; the  resulting  button  of  lead  contains  all  the 
silver.  The  button  is  heated  on  a cupel  or  dish  of 
bone-ash  in  a current  of  air.  The  lead  is  oxidized 
to  litharge  (PbO)  which  sinks  into  the  cupel,  leaving 
the  silver  behind. 


CELLULOSE  AND  VISCOSE. 


125 


CHAPTEE  XIV. 

Cellulose. 

Cellulose  is  the  essential  constituent  of  all  the 
hard  parts  of  plants,  and  its  usefulness  to  mankind 
in  general,  and  to  the  photographer  in  particular,  is 
almost  unlimited.  Jute,  hemp,  paper,  linen,  cotton, 
etc.,  are  all  more  or  less  pure  forms  of  cellulose. 
Schleicher  and  Schull’s  filter-paper  is  pure  cellulose, 
whilst  cotton-wool  and  ordinary  blotting-paper  con- 
tain very  little  foreign  matter.  Pyroxylin,  or  gun 
cotton,  is  a nitrate  of  cellulose,  and  collodion  is  made 
by  dissolving  this  in  suitable  solvents.  Cellulose 
belongs  to  a large  family,  which,  besides  several 
closely  allied  forms  of  cellulose  itself,  includes  starch, 
cane-sugar,  grape-sugar,  dextrin,  and  other  bodies. 
They  are  all  known  in  chemistry  as  carbo-hydrates, 
because  they  contain  carbon  and  hydrogen  and 
oxygen  in  the  proportion  to  form  water.  Although 
their  percentage  composition  has  been  known 
accurately  enough  for  some  time,  the  actual  way  in 
which  they  are  built  up  is  still  being  worked  out,  and 
although  the  materials  out  of  which  they  are  built 


126 


WILLESDEN  PAPER. 


are  so  simple,  the  actual  structure  is  very  com- 
plicated. Cellulose,  for  example,  is  generally 
written  (CeHioO^)^,  which  means  that  chemists  do 
not  yet  know  how  many  CgHioOg’s  go  to  make  up  a 
complete  molecule  of  cellulose.  The  same  is  true  of 
starch  and  dextrin. 

Celluiose  is  soluble  in  strong  sulphuric  acid,  being 
converted  into  glucose  or  grape  sugar,  but  if  paper 
be  passed  through  dilute  sulphuric  acid  of  specific 
gravity,  1’5,  it  is  parchmentized.  Copper  sulphate 
precipitated  as  hydrate  of  copper  by  ammonia  sol- 
ution, and  dissolved  in  excess  of  the  latter,  forms  the 
usual  solvent  for  cellulose.  Advantage  is  taken  of 
this  solubility  in  cuprammonia  solution  in  the  manu- 
facture of  “ Willesden  ” paper.  Thick  paper  is 
treated  with  the  solution,  which  gelatinizes  the 
surface,  rendering  it  more  resistant  and  waterproof. 
For  roofing  and  similar  purposes,  two  or  three  sheets 
of  the  paper  are  cemented  together  by  the  solution. 
Strong  alkalis  and  zinc  chloride  disintegrate  cellulose 
after  a short  time,  but  alkali  of  moderate  strength, 
such  as  15  per  cent,  solution  of  caustic  soda,  com- 
bines to  form  alkali-cellulose,  adding  considerably  to 
the  strength  of  the  material. 

This  treatment  with  15  per  cent,  alkali  is  known 
as  “ mercerizing.”  About  three  years  ago,  Messrs 
Cross  and  Sevan  discovered  that  if  this  mercerized 
cellulose  be  treated  with  carbon  bisulphide  a 
soluble  xanthate  of  cellulose  is  produced.  This 
compound,  which  the  inventors  term  “ viscose,”  has 


PYROXYLIN. 


127 


almost  endless  applications,  many  of  which  are  of 
great  interest  to  photographers,  the  important  point 
about  it  being  that  from  its  solution  in  water,  the 
cellulose  can  be  recovered  almost  chemically  pure. 
The  solid  “ viscoid,”  made  by  coagulating  viscose, 
closely  resembles  “ celluloid  ” (see  below),  and  can 
replace  it  for  many  purposes,  having  the  advantage 
of  being  practically  inflammable. 

By  treating  cotton-wool  with  nitric  acid,  various 
nitrates  are  formed.  To  secure  good  results  it  is 
necessary  to  have  the  nitric  acid  perfectly  dry.  As 
this  is  difficult  to  obtain  in  practice,  a mixture  of 
nitric  and  sulphuric  acids  are  used,  which  produces 
the  same  effect  as  if  perfectly  dry  nitric  acid  alone 
were  employed.  Three  fluid  ounces  of  nitric  acid 
(sp.  gr.  1429)  are  mixed  with  two  fluid  ounces  of 
water  in  a large  beaker- flask,  and  nine  fluid  ounces 
of  strong  sulphuric  acid  (sp.  gr.  1839)  are  run  into 
the  mixture  with  constant  shaking  round.  One 
hundred  grains  of  dry  cotton-wool  divided  into 
about  ten  pieces  are  dropped  into  the  solution  when 
its  temperature  has  fallen  to  150°  F.,  and  allowed  to 
remain  for  7 or  8 minutes,  when  the  acid  is  drained 
off,  the  cotton  being  squeezed  with  a glass  rod  to 
squeeze  out  as  much  acid  as  possible.  It  is  necessary 
to  wash  the  cotton  thoroughly  to  remove  every  trace 
of  acid,  when  it  may  be  dried  in  the  air.  This  gun- 
cotton, or  pyroxylin  as  it  is  often  called,  is  soluble 
in  a mixture  of  alcohol  and  ether,  but  they 
must  neither  of  them  be  methylated.  The  follow- 


128 


CELLULOID. 


ing  are  convenient  proportions  for  making  plain 
collodion : — 

Pyroxylin,  . .1*2  grams,  . 60  grains. 

Alcohol  (*820)  . 50  c.c.,  . 5 02s. 

Ether  (’725),  . . 50  „ . 5 „ 

In  winter  it  is  convenient  to  use  5 c.c.,  or  half  an 
ounce  more  ether  and  the  same  quantity  less  alcohol. 
The  formula  for  iodized  collodion  will  be  found  on 
page  43. 

Celluloid  is  a mixture  of  tri-nitro  cellulose  with 
camphor,  and  xylonite  is  a somewhat  similar 
material.  Other  substances  are  added  to  reduce  the 
inflammability  of  the  first-named  materials. 

Paper  can  be  tested  for  acid  by  pulping  a con- 
venient amount  in  a beaker-flask  with  a little  boil- 
ing water,  and  adding  one  drop  of  alcoholic  solution 
of  methyl  orange.  If  it  turns  red,  acid  is  present. 
A dilute  solution  of  iodine  in  potassium  iodide  is 
used  as  a test  for  hypo.”  The  amount  of  loading 
is  ascertained  by  burning  a given  quantity  of  the 
paper  to  an  ash  and  comparing  with  an  equal 
weight  of  good  filter-paper,  treated  in  a similar 
manner. 


COLOPHONY  AND  LAC  RESINS. 


129 


CHAPTEE  XV. 

RESINS,  VARNISHES,  ETC. 

The  resins  form  a large  class  of  complicated  organic 
substances,  found  principally  as  exudations  from 
trees  in  nearly  all  parts  of  the  world.  They  are 
soluble  as  a rule  in  alcohol,  ether,  and  benzene,  but 
are  insoluble  in  water.  Photographers  use  them  in 
making  varnishes  and  in  laying  a dust  ground 
in  photogravure.  The  resins  of  most  importance  in 
this  connection  are  colophony  or  common  resin,  lac, 
mastic,  dammar,  sandarac,  dragon’s  blood,  anime, 
copal,  amber,  caoutchouc  and  gutta-percha. 

Colophony  is  obtained  from  pine  trees  in  Georgia, 
U.  S.  A.,  and  the  Landes  district  in  Prance.  It 
varies  in  colour  from  pale  yellow  to  dark  red-brown. 
It  is  soluble  in  nearly  all  organic  solvents  and  in 
hot  linseed  oil.  Heated  with  caustic  soda  or  potash 
it  forms  a resinate,  which  is  an  important  con- 
stituent of  yellow  soap.  Specific  gravity  1'07. 

Lac  resin  is  produced  in  many  East  Indian  trees, 
through  the  exudation  of  juice,  caused  by  the  bite  of 
an  insect;  the  red  tint  is  due  to  the  colour  of  the 

I 


130 


MASTIC. 


insect  itself.  The  small  branches  with  the  resin 
on  them  are  known  as  “ stick  lac.”  When  the 
resin  is  removed,  it  is  called  “ seed  ” or  “ grain  lac,” 
and,  when  melted  by  boiling  water  and  run  into 
thin  layers,  as  “ shellac.” 

The  dye  removed  by  boiling  is  known  as  “ lac  dye.” 
The  specific  gravity  of  the  resin  is  about  1*12. 
This  resin  is  soluble  in  all  the  usual  solvents,  and  in 
dilute  hydrochloric  and  acetic  acids,  and  in  caustic 
alkalis.  By  treatment  with  chlorine  bleached  lac  is 
made.  After  bleaching,  it  should  be  kept  under 
water,  being  dried  shortly  before  use,  as  exposure  to 
the  air  soon  renders  it  insoluble.  The  freshly 

bleached  lac  forms  a nearly  colourless  solution  in 
alcohol,  and  is  soluble  in  a hot  solution  of  borax 
and  in  sodium  carbonate.  In  a mixture  of  the  last 
two  solvents,  it  forms  a water  varnish,  sometimes 
used  for  negatives,  etc.  An  excellent  waterproof 
ink  can  be  made  by  rubbing  up  Indian  ink  with  a 
solution  of  lac  in  borax  (water,  1 oz ; borax,  130 
grains;  freshly  bleached  lac,  100  grains;  sodium 
carbonate,  6 grains.)  Ordinary  alcohol  contains  at 
least  5 per  cent,  of  water,  and  as  the  alcohol 
evaporates  in  the  cold  faster  than  the  water,  the 
latter  is  left  behind,  dulling  the  surface  of  the  lac. 
If  heat  be  applied,  however,  the  alcohol  and  water 
are  driven  off  together,  leaving  a bright  surface. 
This  difficulty  is  not  met  with  if  the  lac  or  other 
resin  be  dissolved  in  chloroform  or  benzene,  which 
can  be  used  cold. 


VARIOUS  RESINS. 


131 


Mastic  or  mastiche  is  obtained  from  an  evergreen 
shrub  on  the  shores  of  the  Mediterranean.  It 
occurs  in  pale  yellow  transparent  “ tears/’  is  brittle 
and  sweet-smelling,  melting  at  about  226°  F. 
Alcohol  or  warm  acetone  dissolves  it  freely,  and  it 
is  partly  soluble  in  hot  linseed  oil,  precipitating 
slightly  on  cooling.  Specific  gravity  1*07. 

Sandarac  exudes  from  an  evergreen  tree  in  N. 
Africa,  and  somewhat  resembles  mastic.  It  has  a 
specific  gravity  of  1’04  and  dissolves  readily  in  the 
usual  solvents,  including  hot  linseed  oil. 

Dragon’s  blood  is  obtained  as  a blood-red  exuda- 
tion from  the  rattan  palm.  It  dissolves  in  most  of 
the  usual  solvents  and  in  caustic  soda  and  glacial 
acetic  acid,  but  is  insoluble  in  petroleum  ether, 
(benzine,  or  benzoline),  and  but  sparingly  in  ether  or 
oil  of  turpentine.  There  is  a good  deal  of  variation, 
however,  in  its  constitution  and  properties.  It 
melts  at  about  250°  F.  and  has  a specific  gravity  of 
1197.  In  photography  it  is  used  as  a resist  when 
etching  metal. 

Elemi  contains  a large  proportion  (12j  per  cent.) 
of  volatile  oil,  is  pale  yellow  in  colour,  and  of  various 
origin.  It  is  very  fusible  and  is  used  to  give  tough- 
ness to  lacquers  and  varnishes.  Elenii  is  often 
adulterated,  or  a factitious  product,  consisting  of 
colophony,  Canada  balsam,  and  essential  oils  is 
substituted  for  it.  The  fraud  may  be  detected  by 
heating,  when,  after  a short  time,  the  turpentiny 
smell  of  the  common  resin  is  unmistakable. 


132 


RESINS  AND  BALSAMS. 


Dammar  is  obtained  in  lumps  of  varying  size 
from  pine  trees  in  the  East  Indies.  The  fossil  Kauri 
gum  found  in  Kew  Zealand,  etc.,  forms  another  kind 
of  dammara  resin.  It  is  not  very  soluble  in  alcohol, 
more  so  in  ether  and  completely  so  in  oil  of 
turpentine,  petroleum  ether,  etc. ; it  dissolves  also 
in  hot  or  cold  solutions  of  sodium  carbonate.  Its 
specific  gravity  is  about  1*05. 

Anime  and  copal  are  obtained  from  various 
sources,  some  of  them  fossil,  the  latter  being  highly 
prized.  The  S.  American  resin  is  generally  known 
as  “ animi  ” and  the  East  Indian  as  “ copal.”  Some 
of  the  East  Indian  copals  are  soft  and  are  soluble  in 
ether.  Hard  copal  is  light-brown  in  colour  and 
makes  excellent  varnish.  Its  specific  gravity  is 
generally  between  1’06  and  I'O?.  Before  being 

heated,  copal  is  insoluble  in  alcohol,  and  only  slightly 
soluble  in  ether  or  oil  of  turpentine.  On  heating, 
however,  gases  are  given  off,  and  the  residue  dissolves 
readily  in  ether  and  oil  of  turpentine. 

Amber  is  a fossil  resin,  largely  used  for  orna- 
mental purposes.  It  is  insoluble  in  alcohol,  essential 
oils  and  in  acids,  with  the  exception  of  sulphuric 
acid.  The  specific  gravity  of  amber  varies  from 
1*05  to  ITO  and  its  melting-point  is  550°  F.  Like 
copal,  it  is  changed  by  heat,  and  is  then  soluble  in 
alcohol  and  turpentine  oil. 

The  balsams  are  resins  containing  varying  pro- 
portions of  essential  oils  and  similar  substances. 
Among  these  oleo-resins,  Canada  balsam  is  of 


INDIA-RUBBER. 


133 


importance  to  photographers.  It  is  a pale  yellow, 
transparent  material,  which  forms  a beautifully 
clear,  glassy  varnish.  Canada  balsam  dissolves  in 
benzol  or  chloroform,  and  is  much  used  in  this  state 
as  a medium  for  mounting  microscopic  objects. 

' Caoutchouc,  or  India-rubber  and  gutta-percha,  are 
often  confused,  but  they  are  quite  different  sub- 
stances. Caoutchouc  is  a complicated  body  containing 
several  different  chemical  substances,  and  varies  a good 
deal  in  its  properties  according  to  its  place  of  origin. 
It  is  soluble  in  coal-tar  naphtha,  ether,  chloroform, 
bisulphide  of  carbon,  benzene,  and  oil  of  terpentine. 
Its  principal  use  in  photography,  besides  india-rubber 
tubing,  vulcanite  dishes,  etc.,  is  for  safe  edging 
plates.  Sulphur  combines  with  caoutchouc,  the 
product — vulcanite — being  insoluble  in  any  solvent, 
not  affected  by  heat  or  cold,  much  more  elastic  than 
caoutchouc,  and  generally  more  permanent. 

As  this  is  a somewhat  miscellaneous  chapter,  it  is 
convenient  here  to  say  a few  words  about  oils,  and 
solvents.  Oils  may  be  divided  into  mineral  oils, 
fixed  oils,  and  essential  oils.  Essential  oils  nearly 
all  possess  the  formula  CioHig;  they  are  very 
volatile  and  possess  strong  odours,  which  are  some- 
times due,  however,  to  the  presence  of  other  volatile 
materials,  such  as  cinnamic  aldehyde  in  oil  of 
cassia,  benzoic  aldehyde  in  oil  of  almonds,  etc.  Oils 
of  turpentine,  lavender,  cloves,  peppermint,  etc.,  are 
examples  of  essential  oils.  They  possess  strong 
solvent  powers,  especially  on  resins. 


134 


OILS  AND  SOAPS. 


The  fixed  oils  are  of  vegetable  and  animal  origin, 
and  consist  principally  of  mixtures  in  varying  pro- 
portions of  oleic,  palmitic,  stearic,  and  similar  acids 
combined  with  glycerin.  Alkalies  combine  with 
the  acids,  setting  free  the  glycerin,  and  this  is  what 
happens  when  soap  is  made,  soap  being  oleate, 
palmitate,  stearate,  etc.,  of  soda  or  potash.  Hard 
soaps  contain  soda,  and  soft  soaps,  which  are  generally 
manufactured  from  fish  oil  with  a little  oil  of 
almonds  to  cover  up  the  fishy  smell,  contain  potash, 
but  mixtures  of  soda  and  potash  are  often  employed. 
Most  soaps  are  more  or  less  adulterated  with  silicate 
of  soda,  aluminate  of  soda,  talc,  etc.,  and  water. 
Yellow  soaps  contain  resin ; unless  in  excessive 
quantity,  however,  this  should  not  be  considered  an 
adulterant.  Free  alkali  is  often  present,  which  is 
objectionable  for  most  purposes  except  scouring. 

The  drying  oils  contain  linolic  and  linoleic  acids, 
which  are  acted  upon  rapidly  by  oxygen  if  exposed 
to  the  air,  a skin  being  formed  which  acts  as  an 
excellent  waterproof  varnish.  Advantage  of  this 
property  of  drying  oils  is  taken  in  mixing  paints ; 
it  is  not  the  colouring  matter  of  the  paint  but  the 
drying  oil  that  affords  the  protecting  surface. 
Lead  salts  assist  this  drying  action,  and  a white  or 
red  lead  paint  dries  very  rapidly  and  forms  an 
excellent  protection  against  weather.  The  principal 
drying  oil  is  linseed,  the  following  oils,  however, 
possess  drying  properties  to  a less  extent : hemp, 
walnut,  poppy,  and  sunflower. 


SOLVENTS. 


135 


Castile  soap  should  be  made  from  pure  olive  oil. 
Once  upon  a time  Marseilles  soap  was  made  from 
olive  oil,  and  some  of  it  may  be  still,  but  the  greater 
portion  of  the  Marseilles  soap  in  the  market  is  made 
from  all  kinds  of  oils. 

Beeswax  is  the  principal  wax  employed,  but  it  is 
adulterated  with  paraffin,  Carnauba  wax,  and  Japan 
wax.  Paraffin  is  used  largely  as  an  adulterant, 
and  may  be  detected  by  treating  the  wax  with  oil 
of  turpentine,  which  dissolves  the  beeswax  and 
leaves  the  paraffin. 

As  regards  solvents,  two  of  importance  are  fre- 
quently confused : hQuzene  and  benzme  are  quite 
different  bodies.  The  latter  is  light  petroleum  oil, 
sometimes  called  petroleum  ether,  whilst  the  former 
is  the  active  constituent  of  coal-tar  naphtha.  Crude 
paraffin  or  petroleum  oil  contains  a whole  series  of 
bodies  known  as  paraffins,  the  lowest  of  which  are 
gases — marsh  gas  (CH4),  ethane  (C2Hg),  propane 
(CgHg),  butane  (C4H10) — then  come  volatile  liquids, 
beginning  with  pentane  (C5H42),  each  member  of  the 
paraffin  series  differing  from  the  next  by  CH2,  then 
the  burning  oils,  then  the  heavy  oils — solar  distil- 
lates, used  for  enriching  water  gas  — then  the 
vaselines,  then  the  lubricating  oils,  and  at  last  solid 
paraffins  or  paraffin  wax.  Benzine  or  benzoline 
consists  of  the  paraffins  following  and  including 
pentane  ; all  the  liquid  paraffins,  however,  possess 
strong  solvent  powers  for  grease,  resins,  and  many 
other  substances. 


136 


ALCOHOL  AND  ETHER. 


Benzene  is  obtained  by  refining  light  coal  tar  oil 
and  is  perhaps  the  most  important  compound  known 
to  chemists.  It  contains  six  atoms  of  hydrogen 
united  to  six  atoms  of  carbon,  and  acts  in  all  its 
properties  and  derivatives  as  if  it  were  joined  into 
a six-sided  ring,  as  shown  on  p.  57.  It  is  some- 
times called  benzole. 

Chloroform  may  be  considered  as  marsh  gas  (CH4) 
in  which  3 H’s  have  been  replaced  by  3 Cl’s,  its 
formula  being  CHCI3.  It  possesses  great  solvent 
powers,  especially  for  fats. 

By  Alcohol  is  meant  ethyl  alcohol.  The  alcohols 
form  a series  in  the  same  way  as  do  the  paraffins, 
being  derivatives  of  the  paraffins.  For  example, 
ethane,  by  a round-about  chemical  process,  can  be 
converted  into  ethylic  alcohol,  thus : 

Ethane.  Ethylic  iodide.  Ethylic  alcohol. 

CH3.CH3  CH3.CH2I  CH3.CH2OH. 

From  ethylic  alcohol,  ethylic  ether  or  “ ether  ” can 
be  obtained  by  removing  a molecule  of  water  with 
sulphuric  acid. 


By  oxidation,  alcohol  is  converted  into  aldehyde 
(CHo.COH),  and  by  further  oxidation  into  acetic  acid 
(CH3.COOH). 


Ethylic  alcohol. 


SOLVENTS  AND  VAENISHES. 


137 


From  acetic  acid  another  solvent,  acetone 
(CH3.CO.CH3)  is  obtained.  It  is  a powerful  solvent 
of  most  organic  substances. 

Methylated  spirit  has  crude  wood  spirit  added  to 
it  for  the  purpose  of  making  it  undrinkable,  so  that 
the  material,  as  sold,  contains  ethylic  and  methylic 
alcohols,  besides  acetone  and  various  resinous 
materials. 

It  is  interesting  to  note  that  pure  methylic 
alcohol  is  the  lowest  of  the  series,  being  based  on 
marsh  gas  (CH4)  in  the  same  way  that  ethylic 
alcohol  is  based  on  the  next  member  of  the  series, 
ethane.  By  similar  treatment  to  that  given  above, 
methylic  alcohol,  methylic  aldehyde  or  formic  alde- 
hyde, as  it  is  usually  called,  and  formic  acid  are 
obtained. 

Carbon  bisulphide  is  a compound  of  carbon  and 
sulphur  (CS2).  It  is  used  principally  as  a solvent 
for  india-rubber. 

The  following  are  useful  formulae  for  varnishes  : — 

Amber  Varnish  {Abney). 

Fused  amber  (powdered),  . . 1 part. 

Chloroform,  . . . . .16  parts. 

May  be  used  cold  for  plates  or  prints. 

Collodion  Varnish  {Gamble). 

Pyroxylin,  ...  2 grams,  100  grains. 

Ether  (methylated),  . 50  c.c.,  . 5 ozs. 

Alcohol  (methylated),  . 50  „ . 5 ,, 

Castor  oil,  . . . 0'3  ,,  . 16  minims. 


138 


VARNISHES. 


Varnish  for  Collodion  Lantern  Plates  {Photogram). 

Dammar,  .....  1 part. 

Benzole,  . . . . .20  parts. 

This  varnish  can  he  used  cold. 


Lac  Varnish  {Cooley). 


Seed  Lac  or  Shellac,  ...  4 parts. 

Rectified  spirit,  . . . . 20  „ 

Clear  Mastic  Varnish  {Phoiogram). 


Mastic, 

Canada  balsam,  . 
Sandarac,  . 

Oil  of  turpentine. 


14  ozs 
2 „ 
6 „ 
44  „ 


Shake,  and  stand  till  clear ; filter. 

The  mastic,  sandarac,  and  turpentine  oil  must  be 
dry.  The  longer  it  is  left  before  use  the  better. 


Gold-Colored  Lae  Varnish  {Cooley). 

Ground  turmeric,  . . . . J lb. 

Rectified  spirit,  . . . .1  gall. 

Macerate  for  a week,  strain,  and  squeeze  off,  and  add — 

Gamboge,  . . . . . f oz. 

Pale  shellac,  . . . . .6  ozs. 

Sandarac,  . . . . - If  Ihs. 

When  dissolved,  strain,  and  add  further  of  turpentine 
mastic  varnish  (last  formula),  1 pint. 

This  varnish  is  suitable  for  picture  frames,  brass 
and  other  metal  work.  The  colour  can  be  altered 
as  desired  by  varying  the  constituents.  By  substi- 
tuting dragon’s  blood  for  gamboge,  a deep  gold 


VAKNISHES. 


139 


coloured  varnish  is  obtained.  It  is  a good  plan  to 
keep  the  colouring  matters  separate  in  concentrated 
solutions  and  add  them  as  required. 

By  using  annotta  instead  of  turmeric,  and  dragon’s 
blood  instead  of  gamboge,  a red  varnish,  suitable 
for  wood,  is  obtained. 


Ordinary  Spirit  Varnishes  (Thorpe). 

I.  Brown  hard — 

Sandarac,  . . . . .3  lbs. 

Pale  shellac,  . . . . . 2 ,, 

Methylated  spirit,  . . . .2  galls. 


Dissolve  and  add  1 quart  turpentine  mastic  varnish. 
Agitate  well,  strain  through  gauze,  and  after  one  month 
decant  off  clear  portion. 


II.  White  hard — 
Sandarac, 

Camphor, 

Pounded  glass. 
Methylated  spirit,  . 


5 lbs. 

2 ozs. 

3 lbs. 

7 quarts. 


Dissolve,  and  when  strained,  add  1 quart  pale  Canada 
balsam. 


All  the  above  are  “ spirit  ” varnishes.  An  “ oil 
varnish”  contains  a drying  oil  in  addition  to  the 
resin  and  other  constituents.  The  following  is  a 
good  oil  varnish  suitable  for  wood-work,  etc. — 

Pale  hard  copal,  . . . .2  lbs. 

Fuse  and  add 

Hot  boiled  linseed  oil,  . . .1  pint. 

Boil  until  stringy,  and  thin  with  about  3 pints  oil  of 
turpentine. 


OTOLOP^DIO  INDEX, 


140 


cyclop.^:dic  index. 


s § 


§ s 


rC) 


■>. 


k-i  d ^ 

S & 


tn  w 

> “ <X>  > 


CO  c/j  § CO  O 
|>  > ^ > CO 


OOO  (M<N^§g«5g 

iO  CO  ?0  O 05  2 2 'Cfl  I' 


VO 

l ’^  ^ 

(N  «5 


W c, 

oQ. 


O o 
W M 

c oo  c^  + 

ooQ.  « + o 


O Ph  CQ  O O CQ  O 

0_- 


CO  (M  <or 


WM 

o 


o 

^ W 

l-H  ^ 


PP  * 

hn  (N 

K 


" -2  ’ -rT 

^ -3^  .2 

^ ^ .2 

^ ^ o 

• •^  ° • • p 

c'S  -2  rs  -'-^  "3  >-i 

^ CS  o 2 .2  ‘5^  ffi 

05  +3  ._4  C 2 <-H  " 

.2  “ o ^ S'®  ^ 

, W . S ^ 

o 

t-  2 

"-S  -ss i -sg 

05'' 

rH 

m 

:=J 

• o • 

.2.2  '3 

O O r2  .2  'p< 

'-M  .2o'^  fc-.^ 

'05  .2  rt  '3  "o  o ® M ’-^ 

05  in  2 2 2 o .2  ‘3 .2  2 2 ‘C  o .2 

o - 0^3^. 'Soc^ 

■S3  pquQOOPi^^O  W W WW!^ 

C5  a 
^ <! 


CYCLOPAEDIC  INDEX. 


141 


O Z3 

o>  S • M 

-c  ^ > 


o 

00 


a 


d 

T3 


. . o . o . . 

flCOOajM  . . .o  ' c a • 

C 1-1  ® >•  <N  C S 


o 

lO 


• <=> 
c<l  M 


• a 


• a a ” a 


1^ 


tn 

> ^ 


c*3r^'®oo^  .ooco^^cocMO 

ooo^Jf^-^coco  ^ 


I—  o>  o» 

05  O O 05 

CM  05  05  05 


05 


o 

w"  o” 

«0  « C<)  rf  ?? 

OO  +Offi 
X,  X 


WW 

QK 


+ 


(M  ‘ 

^.is 

tew 


teo 


te 


' 

o3 

o 

g a 

o 

. w 


a|^ 

^ 'a  ^ 

S M g M 

s'^.a 
a fl  ^ 

o o o 

,o  w w 


' • a 


CO 

CO  i-( 
CO  CO 


o 

CO  CO 
CO 

05  (M 
^oo  CO 

Tji  ^ 

o-  00*' 


(>J  § 

CO  CO 


(M 

CO 


t-l  T 

o :z 

ra  :s ; 


- ...  .a  a> 


=D  >1^  pO  a ci ^ 

.-^  cn  o O O-0j”.3’7^+^  5>. 

p3  O 5h  r!^rX  O ^ 2 C5 

WoSphc^mkEhh  8 


W a 

'--.a  ^ 


Ja 

■^l-S 

.-I  ' — ce 
o3  2 O 

.2  rs  P-i 


O 


. CO 

a 

o 


I c3  O A- 

i 'a  'a  i 

' O O c 

s a ‘ 
a a 


142 


CYCLOPAEDIC  INDEX. 


■e 

Cold 

lcoh( 

M CO  g ^ M . 

lO  CO  . . . 

C<)  Tj<  M CO 

• 

Pk 

o 

fed 

a 

Boilin 

Watei 

422 

vs. 

dec. 

73 

vs. 

VS. 

vs. 

vs. 

s. 

vs. 

200 

'o 

Cold 

Water. 

_ 00  lO  lO  M . 
^ (N  CO  ►> 

165 

200 

33 

s. 

105 

<^  . . . 

130 

Molec- 

uJar 

Weight. 

253 

98 

175 

52-5 

37 

35 

145 

80 

143 

51 

76 

124 

CO 

• • CO 

CO 

o 

Symbol. 

o',  o 

W ffi  ::a  H? 

£•  S 

<N 

^ CO 

o®  9. 

ffi  ’T’  -ri.  ^ 

SmoWw 

W - 

W 

o • • • 

W 

CO 

W . . . 

CO 

O 

• • ^ 

w 

(N 

+ 

PQ 

. . 

« 

o 



o 

-2  S 

o 

§ 

'o 

eg 

S 

i 

- 

o 

S 

np 

E3 

1-5 

s 

S 

■ ■§!  ‘I 

s 

'*  ’ * * .2  ■ 
'S 

A 

D ^ . 

4-3  O 

pS 

k-< 

o • 

p 

03 

o 

g-?  I' 

(D  C6  ^ 

see) 

mmo 

=«  ‘S 

a 

p 

• • CO  cy2  . <I 

. . . .<1 

. . 

w . 

o 

o 

\a 

CO 

I— t 

o 

Oi  (M 

Refere 

Page 

44 
32,’ 4 
32 

■^  . . . ■^ 
Oi 
to 

<»  (M  (N  r-H 

„CO  i-i  ..T-H  ^ 

00  »-t  rH  i-H 

to  O 

T— 1 

81 

132 

Oi 

1 

o 

03 

■ " 03 

Name. 

.o 

^ (D 

Is 

'S 

cd 

03  ^ 
p 

s 

• -i:  • 

a . 

w S 
MU  1 
?■ 

§ 

g kH  ^ .Ji:  S 
1 WOOPtH  W 

lodidi 

Nitra' 

Oxala 

Sulph 

Sulph 

^ 0^  o 

O 03  P -M 

S S.BPS 

a ‘P  rQ 

P P f-l  M 

-J-3 

Pk  o 

03  -M 

bO  2 rH 

.a  2 g 

^ ce  P 

WWW 

CYCLOPAEDIC  INDEX. 


143 


MOT.  • .«; 

OT  >.  • 

OT  • . . 

r->  • CO 

OT 

CO 

W . 

CO  . 

VO 

oo 

CO  o • 

^ n3 

>•  I— I rH 

CO 

40 

vs. 

i. 

i. 

• 

CO 

w . 

w 

1-06 

160 

90 

o . 

1 — 1 

132 

0-137 

ss. 

rfH  lO  Oi  no 

'5ti  (M  oH  <r>  • 

05  «0 

o o 

05  ^ 

« ' ' ■ 

r-H  . 

o o 

T-H  CO 

c^  Tj<  CO  i-H  ^ 

CO  CO  CO 

CO  l-H 

CO  r-H 

_ O 

9.0^ 

w a oo 

, 

oo 

w w 

M CO 

O 

^ j_  C«  CD 

+?i?« 

Br 

CO  (N 
+ +!^ 

^ O 

^9 

?oOo 

(nOPCO 

r ^ ^ 
O r*^ 

CQO 

t; 

QO 

o 

• • Cfl  • • • 

-M 

rfi  rQ  ^ § 
cd  eg  ^ ^ 

• • qJ  q5  • • 

II 

&£ 

.2 

+5 

• ' __  3 

oT-^ 

S ^ 

rO 

T5 

•5  --I  o o 
o ^ 

p 

^ ;s 

a> 

IB 

— A- 
05  ^ JJC 

Crystallise 

Benzole  . 
Benzoline 

•jili 

III! 

<50 

. Co  Cq  Cq  Cq 

• • § ' ' 

.::i 

§ ^ 

. .^>2  CQ  . . 

rO 

. . . ^ 
•S 

Chalk,  ' ■ 
plaster 

Slaked  lim 
Chloride  o 
Bleachin 

»o 

Tt(  o 

Tt< 

• • • • CO 

(S'~' 

o 

22 

o-t2  O oO  „ 

CO  ..  2 -05 

.,05  ^ 

05 

IT5  =C) 

O O rH 

611 

o • • 

o3  3 

o £ 

* <D 

S 


„ ^ a> 

® CD  -U3 

T5  • ■ ce 

'x  ® 0.'^  O 


S=S’S.2i.SSi  . 
■=.2KdiSS-S  i'- 


03  .r< 

5^:2 


o q:>  <D 


5 o .zi  -MM 

^ 3 S fi  ^-S-2 
.:s.2  2 2 2 3 3^ 
cqpQCQcq23«fCW 


a>  ® (u  .— 
WPQWPQ 


QJ 

'X3  . . . 


144 


CYCLOPEDIC  INDEX. 


•1 1 

o 

2 ° 

-H 

O O 

CQ  *f4  * . 

« ' • • « 

1 

Ph 

■< 

o 

bo 

o 

C 

>> 

Boilin 

Water 

450 

• ••-  • • • 

2 

o 

CO 

Cold 

Water 

200 

• -*  • • • 

. . . o 

^ o3  bO 


d ci 

oo 


o cc 

o 


c 

o 

o 

<o 

o 


Q 


<D  CD  O 

2 


ri 

C? 


. cc 


o ^ 

a i 

1 1 

M JI3 

• 

J o O 
P-i  cc 


Cc  Cq 


TJ  T3 

rC  ^ 

• CO  a 

CO 


A ^ 

PM  OT 


TO  ^ 

O § 

>5^ 


a 

. 


cfl  O 

• ^ 


<H  P-l 

« 


CO 

CO  40 
O CO 


O^.go, 

«0  o S 

CO 


(M 

„ CO  lO  00 
O (M 

CO  rH  I— I 


<D 

T3  (33 

‘S 

o § 


03  (D 

s a 


:s  o 

I ^ 


8 g 


■s 

o o 

Ph  CO 


!■: 


ooo  o 


o3 

Q 


0 0-13 


O d § 
'TD  ^ 

rJ  ^ PI 


OO 


'o 

Ph  =3 

(D  rP 

OQ 


_o 


CYCLOPAEDIC  INDEX. 


145 


20 

vs. 

vs. 

203 

dec. 

. CQ  0 os 

^ > CO  CO 

09 

. . .» 

>p  'P 

-p.  0 CO  0 OS 

S 0 (M 

^ (M  (N  i-H  (M 

10 

<N 

o 

w oq^ 

+ M W 

CO  e.,  (nMh  ^ 

^ 6 -f  ^ 4. 

OMQO„^t  + 
o ffiO 
Q 


qS 

OQ 


0 

s' 

0 

* ' • cn 

■ ® — 
“ .2 

< 

0^  .'2 

!-< 

CD 

,B  ^ 

.S 

<M 

\a 

136 

33 

. 

126 

O 


’-'2  2 ,-H  ,-( (M  rH  t;- 

<:d  ^ 


<D 


c3 

(D 

B S 
o o 


CD 

..-I 

ci 


gj  CD 


I AS 

c6 


CD  CD 


^ TO 

^ rH  C3  r=! 


. OT  bO  o 

^ .s  ^ 

.2  t^rTj  2 


4,  O)  o ’— 2 


OOOQ 


O <D 


;3 
0 02 


” ^0- 
fc/j  ~. 


o o 

00 


fD 


■ 8^ 
00 


Pu  Ph.^2  o »-' 

M CO  0H  ct5  Y C ^ C 

S 'T5  ;!,  .S  -P  .5 

S -g  ^ 3h  3 5 .5 

Qi^^i=3r^r8,S  3-+J  3 3- 
00000  00 

00000  00 

K 


o W 

r8 

'o  ‘o 


00 


146 


CYCLOPiEJ>iG  INDB^. 


00  ^ CO  § 

coco^w^o 


-?0  »0  «o 


'TJ 

a 

o 


a 


o 


|.S  » 

t-i  c 2 

3 >>  O 

QOQ 


g 5 9 °3 

^ to  a 

POP 


5^-3SU.2.a-^  ^^-§3 


fl 

03  O ce 

d o 2 § ft « 


. 03 

d 

o 

2.5 

.3  ^ 

s]  cr* 
(S  O 


03  03 

PP 


I-I  '-'  Sh  d o nj.rrt 

d^ 

I — I f— 1 03  03  ^ a ® 1-^ 

PnPL(t>><l<<WpE<  OWW 

03  03 

PP 


CYCLOPEDIC  INDEX. 


147 


o 

Q 


o CO 

’T}  , ® 

‘a  CQ. 

5 0) 

cS  • (D 

^ 4J O 

o 'rj 

§ I 

TU  C P.  ^ 

o P 

■ 02  W 


e ° 
o .: 
*+ 
o 
o> 

' 

3^5 


lO 


oo  ^ 
rtt 

CO 


I 

I ta. 


o 

C TJ 

' O .-H 

P3  O 


T3  ;z: 


cS  cS 


B tea 


0)  Q 

g 2 T3 
13  ce  t>j  o 

> &H  pH 


'o 

>> 

’xi  ’ 

c -c 
2 o 
'S  o 

rS 

? «.s 

E 

; expt. 
g plates 
ogen 

0-chemisl 

ting 

)ing 

nts 

ions 

rosin 

thylated 

SrS 

^ O fH 

“J 

O 

3 §D-i^ 
^ ^ 

"Z  p « 

8 Ph  H § ^ ’g  ^ 

2 

P V 
S © 

pq  p^  fiq  pq  pq  pd  pil 

P3^  p^ 

148' 


CYCLOPAEDIC  INDEX. 


T3  S 
"o  O 

<1 


o CO 


2 .ph‘  O . j CO 


. g . . 


Oi  — - 


^ cq 


O O 

ta  ■ 

0+0  t, 

X^^vo  ^ o 

PH  ^ pc.  * 


K 

o 

o 

o 

. M (J, 

Wg 

oR  p 

o 

<o 

o 


Pa 

X 

,o 


.Si  rt 
<u  Ph 
Ph 


os  o4 
(N  <pq 


- V® 
j>-  lO 

00  o'' 

?o 


^ O CO  ^ Q 


^ o 

-5  3 

>,  <o 
,P  w 
.2§ 


ca  <D  • 
ca  P 

o., 


O ^ X X |ZI  ^ 

hMOOj^^- 


g 

_x  _x 

E S 


S >: 


O 


rQ  P-  Pa 


o 


o| 

§=£ 


o 

S _ 

9 "o 

O P 

3 ^ 


-7; .p  fl .:. 

+3  eg  +0  O 
H P— I ca  *rS  <s 

ca  'o3  42  'P  ? 

00  O OoOOOO 


CYCLOPyEDIC  INDEX. 


149 


CO  CO 

O >-1  Oi 

CO  CO 


(M  ^ 2 

CO  CO  I-H  CO  Oi 
^ CO 


o 

<N 

w ... 

(N 

-i- 

- „K  a®. 

o 

^ ... 

B 

o' 

. B 

B B 

03  "‘5 
'2  ^ 

c3 

• j-(  ^ O 

Bo  “ ^ 

° Q,  03  03 

2 'B  ^ 

§2 

£ 

O >-H 

CO 

“ 3 

2 3 3 

o 

s 

B qp 

B B 

O 

5 

oo 

>> 

T} 

s ■ “ • 

O a 

o 

ts  fc:  «> 

B 

''3  CD  cS 

^ C c M 

o .2  2 

-S  ‘ 


'-*:.  o 


^ <D  TO 

:i:^  4^  o3  ?H 


® c:2 

• rt  c:’  t.<' 


, . 03  . 

<D 

<D  B *-1^ 

B -BO 

s^li 

cr^  M >0  rrt  o 

p p P ^ P^ 


BT;'B'T3i2'^'^'^lllhr( 


WpqKWffiffiWW  WKffi 


rB 

CB 


w 


w 


Sollibility  in  100  Parts  of 


150 


CYCLOPAEDIC  INDEX. 


o o 


si 


o> 

CO 


o « 


J:;  « 


!>•  i-^ 

O • CO 
<N  CO 


CO  I-I 

CO  (M 

I c<J 

OO  ^.-1  (M  r-( 


S S 'd'oo 

^ QO 


a 

ci 


^ bO 
.2  C 


c3 

a 

Pa 

ci3 

(/} 


^ ^ O ^ .S  i=! 


.2  .2 


p 

c6 


si  o3  I 

O)  QJ 


2 ^ 

."tH 

'►2 


CYCLOP JRDrc  Tl^DEX. 


151 


. . . . (jj  . 

....  CO 

CO 

• • '•  '•  oJ 

• 

. . . 

[ 

i 

, 146 

kO 

• • • • CQ 

• 

. . . 

. . . . . 

00 



• • • * CQ 

• 

• . * 

7 

42 

O I-I 

. . . . O 

<N 

rH 

. . . 

q 

Li  * 
LiCl 

04 

Uh  ^ 
W 

. w 
§ 

w 

q 

12; 

• • • 1 

o 

. . . . . . ® 

i=i  'TJ 

. . . o 

’§ 

^ Si 

Quicksilver 
Corrosive 
mate,  Bit 

g . . . . ^ 1 

0>  *■  ^ 

S 

•S  1 a 

. S 

114 
32 
7,  9 

75 

130 
11 
7,  8 
122 

84,’l05 

. t>.  00  nn 

O 

r-i 

CO 
CO  rH 
CO  CO  .. 
rH  l-H  OO  j 
CO  1 

r— 1 

tS3 

% 

<D 

Oi 

a 

. bO  ...  . 

. . 

, 

Line  engraving 
Litmus  paper 
Litre 
Lithium  . 

Chloride 
Lumiere  and  St 

M 

Mastic 

Mathematical  si 
Measures 
Mercerising 
Mercury 
Perchloride 

Yapour 

Methylated  spii 
Ether 

Methyl  orange 
Metol  . 

1 N 

Nitrogen 

i 

0 

Oils,  drying 
Essential 
Fixed  . 

152 


CYCLOPAEDIC  INDEX. 


'as 


O O 

. 0?  a>  • . 
® 


W). 


'II 


c5  CN  ?o 
' Q^goio 

tH  1—1 


s s 

■s| 


, « <N  CO 


« t 

5 


o . 


_ 0>  00 
S OS  rH  CO 
*”  (M  r-H  rH 


Cl 

w 

q 

W 

w" 

o 

o 

Mrf«8 

w 


-H  O 

es  ;::5 

fl  o 

S -P 


Q)P-I 


00 

” tCo'*'® 

CO  1-1 


OO  <©  )0  _ 1 


. O rH  ; 


Il<  Tt<  I-H  2 «o 
(N 


• a 


•rt 


p 


.s  ^ 

r— 

O ^ 


• ba 
d 

CO  "d 
o a> 

.d  ^ ^ 

t^  ’«  ‘x 

ooo 


m 

d Ps 

<D  ci3 
&0 

X 

O 


-^2  d'-iS  P 
^ <D  drP 


1,^ 

o3 

Ph 


Pa  . ce 

S -M 

X d P 

■-*  ® o - a 

I a-'i  ill 

.;H  C«  O)  H 
-M  ^ Ph  N ^ .1^ 

O ooo 

Pa  CL|  Ph 


« ^ rH  -- 

M 'S  o o 

S o . S 

O nK  -te  d 
^ d <x> 

^ g _ 

1i  C3  <D  "cP  •tt'.PI 

Cl,  Pui  Ph  Pa  Ph  P-i  Ph 


g§ 


J w 


:a  c 
a,S 
2 

WQ 


CYCLOPAEDIC  INDEX 


153 


^ M ^ *=> 


S5?S  »• 

o 


?D  § CO 

CN  g CO 


^ CO  Tf  Oi  05  05 

;^OOC5g  05  05  g05 

CO  'r^^  ^«05 


>> 

0 

w" 

• • 05 

. 

• • 

§S'5.| 

««g 

M 

0 

® 

Ph 

eo 

M 

CO 

+ 

CD 

>5 

0 

r® 

Pm 

la 

WO 

Om 

w 

0 

§ 

<0 

. .0 

w 

0 

w^ 

•JO 

. . .0 

M 


1 <t-t 

> 0 

S3 

, -S 

cTD  Jh 

' .2 

• -H  0 

1 CQ 

OT 

c3 

s s 

! § 

rC  2 

c£l 

' OT  ^ OT  .. 

• ® ,0 

6 ^ 

- ^ 

.2 

-M  ^ 
0 CC 

2 S, 

1 (=4^:3 

PM  P 

3 § 

1 ® 

o3 

® 

1 >H 

0 

.0 

I’fe 

p ? 


1C5 


1-H  05  « 

^O  05  CO 

lO  1-1  »-i  CO 

S 05" 

05  j>. 


05 

O 


oT 

J>. 


05  CO 
CO  iO 


00 

05 

-rtT 

05 


05 

«o 


i>r 

iO 


r2  .S 

'"S  -2 

§ o |:§ 

.1^  o o 5 
M f-.  c3 
>, 

-2oqo 


® 

® 

® 

* ••-1 
rP  ce 

3 

3 

3 

cS 

3 

c3 

® OT  g 

(>5 

0 

P 

33  ? 
2 3 fco 
^3  3 

Pm 

s 

Pm 

W3.S 

g'S  2 
2 3 >> 
PhPwPh 


P5 


fcc 

.S  2 -a 

o o ^ g 

O 

“ T;  CO  OT 
(D  O 0^  <D 

PhPh  M 


154 


CYCLGl’.^DIC  mmx. 


ai 
^ 

bo  .• 

c S 

0{5 

3Z. 

§1 


.p5  J 


^ ^ ^ 


rd 

3 dj 

CO  ^ 

.l « 

• E3  o 

"§l 

^ o3 

. 


O)  o> 

Sn  “ 
,£  <a 
« CM 
P5 


T— ( CO 

(N  C<> 

01  g O ^ T-l  Co"  C<T  IC5 

(M  1-1 

(N  C<) 


CO  ^ 

, «o  CO  ^ 
00  c<j  ^ 

C<J 

<M 


V)  'T3 
a>  o 

PhPh 


C3  M 

m g 

rQ 
O C3 


(D 


<D 

o3  Ph 
rrd 
P rP 

CS  O 

M GO 


S. 

^ CB 

t>io'-^ 

p p 


o P rP  S 
-t^PrP^C3M(rO-^g 
^ — * C^I— ' 05*^  ^ ^ 

><1PPPP 

o>  o)  m3  :gh 

CO  maiai 


^ 3 


<D 
(D  tP 

rs ® 

<3  P T3 

is  0^  -P 

o ►-H  *3 


CVOLOPi^DlC  IN'BEX 


155 


' i>  ••4  ^ ••4  .4;  ..4 


.,4  ot> 


5 


c5  6 oo 

QJ  CD  1-H  ^ 


<M  2 lO  Oi  «3 


o 


o o urs  lo 

® r-iCXD^ 


»o  «o  o 

CO  CO  CO 


s si 


CO 

(M  OO 


S OO  <i>  00  00 

^ lO  OO  00 


(M  ^ (M  (M  t-h  so 
CT  (M  lO  00  ^ 

CO  (M  Ttt -CM 


o' 

bc 


o^ 


>-*  g W 2 S cT 

+ 20  0^03 
^ 3 M cT 


15 


O) 


. O M “ “ O 

o ^ 01 

1^11  ^ S 3 

3 O cS  03 

• <I1  ^oow 


*-5 

4-s  t3 


O I 

■ ^.2 

43  O 


o 


o ^ 
o 

“ 'S.r 

O) 

Q.  55  ,42 

.ir  o ^ 

43  C4  o 

r3  O,'" 


o ^ ^ ^ CO  ^ „1-I  CD  ^ 

'>’4j3^CO00C02^^rHCO'cti  ooCO  <^00 
~ CO  CO  •t-H 

0 CD 

01  — 


■ CO  CO 


'Cf  O O OO* 
C<J  CO  UO 


^ ' 

"o  I 
o 6 

^ -i-S 

o 

ds: 


43  . Orrt  S 


^ s =« 
42  3 
44 


I PQ  O 


>> 

w 


(D  o)  3 'ri 
■Ti  -t^  43  >-0 

o o 


\ 9^4= 

'B 


’'Or^  P-(  34 

oK  Wffi  W 


IS 


d3 
VI 

o 

'B  ^ 

K H 


156 


CYCLOPEDIC  INDEX. 


6 J 



bD  . 

•S 

II 


<N 

CO 


I 

® s 

Oft 

-S3 

ta  w 

.S  o 

M 


u bo 

C5  ^ 

04 


n~i  1— I ^ ^ ^ r\i 

00  tC  ^ 

lO  r-l 


C<JCO'^'^lOrHC<J»Oi-l  lO 
T-l(N'^TjHTil?OO5l>.00^»i:5 


• ' • S • d • 

.2  O 

gl  § 

a 3.  § -^  „r  • 

El  d 3 

g -fH  M rd  rd 

2 2 <D  o ri  -Ti 
o P-i  P-HJ  +3  d d 
xnmmmmmm 


Eh-S 


> o 

:d  f-i 

cc  W 


i 03  ' 

]'§,' 
T3  ' 
o : 


CYCLOPAEDIC  INDEX. 


157 


o 

CO  . 
(M 


O 

^ . 


T— I Cq  I— I rH  CO 

CO  CO  rH  GO  00 

o 


CO 

00  oo 


r-Ht^OOOOOOOOOiOi 

ocococococococo 

t-H  i-H  I— I rH  »-H  T— I t-H 


. 


<D  ~ 

.?  § 2 .S  - bJD*4^ 


S ^ ^ ^ ^ .2  o 
H H H ^ H H H 


^ a rB 

S -•''2 

Op  2 


03 


cn 


bO  bO 

.2  2 


C3  ce 


[Solubility  in  100  Parts  of 


158 


CYCLOPAEDIC  INDEX. 


^ 

as 


I ^1 


o 

o M CC 


O O . 
•-0  (N  W 
CO, 05  > 


O U5  01 
S CO  CM  r-l 
^ rl.CM  CO 


c»  S’ 

^ ._r  Vh  (N 


CO 

05  -rji 

r— H 

05  ^ rH  C<r 
^CM  ^ 00  Tt< 


§§5 


® 

,N)  rM  Q 


>5  C O ^ 

^ O t-|  Q. 
05  05  05 

-)-3  . -|J  -M  4J 

c3  ^ cS  ca  ^ 
r> 


s: 


3 2"^ 

§OPQ  ° 


NEILL  AND  COMPANY,  PRINTERS,  EDINBURGH. 


LIST  OF  BOOKS 


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i ^ 


namAL  or  in/truction 


IN-= 

HARD  SOLDERING. 

HARVEY  ROWELL. 


CONTENTS. 

Introduction.  Utensils  and  Chemicals. — The  flame.  Lamp.  Charcoal. 

Mats.  Blowpipes.  Wash-boitle.  Binding  wire.  Borax.  Chemicals. 
Alloys  for  Hard  Soldering. — spelter.  Silver  solder.  Gold  solder. 
Oxidation. — Oxidation  of  metals.  Fluxes.  Anti-oxidizers. 

Structure  of  Flame. — Oxidation  of  gases.  The  cone.  Oxidizing  flame. 
Reducing  flame. 

H^^at. — Transmission.  Conduction.  Capacity  of  metals.  Radiation. 
Application. 

The  Process. — The  work  table.  The  joint.  Applying  solder.  Apply- 
ing heat.  The  use  of  the  blowpipe.  Making  a ferrule.  Joints. 
To  repair  a spoon.  Difficulties.  To  repair  a watch  case.  Hard 
soldering  with  a forge  or  hearth.  Hard  soldering  with  tongs. 

• Technical  Notes. — Preserving  thin  edges.  Silversmiths’  pickle.  Re- 
storing color  to  gold.  Chromic  acid.  Steel  springs  to  mend. 
Sweating  metals  together.  Retaining  work  in  position.  Making 
joints.  Applying  heat.  Preventing  the  loss  of  heat.  Effect  of 
sulphur,  lead  and  zinc.  To  preserve  precious  stones.  Annealing 
and  hardening.  Burnt  iron.  To  hard  solder  after  soft  solder. 
Properties  of  Metals. — Tables  of  specific  gravity.  Table  of  tenacity. 
Table  of  fusibility.  Fusibility  of  alloys. 

56  Pages,  12mo,  Cloth,  Price,  75  Cents. 


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Now  rmdy.  Containing  702  pages,  Svo,  cloth,  with  1420  illustraMons. 


SPONS* 

MECHANICS’  OWN  BOON. 

A MANUAL  FOR 

HANDICEAFTSMEN  AND  AMATEUKS. 


The  title  of  this  work  almost  suffices  to  indicate  the  character  of  the 
contents.  The  various  mechanical  trades  that  deal  with  the  conversion 
of  wood,  metals,  and  stone  into  useful  objects  are  explained  from  an 
every  day  practical  view. 

The  method  of  treatment  of  each  branch  is  scientific  yet  simple. 
First  in  order  comes  the  raw  material  worked  upon,  its  characters,  vari- 
ations, and  suitability.  Then  the  tools  used  in  working  up  the  material 
are  examined  as  to  the  principles  on  which  their  shape  and  manipula- 
tion are  based,  including  the  means  adopted  for  keeping  them  in  order, 
by  grinding,  tempering,  filing,  setting,  handling,  and  cleaning.  A third 
section,  where  necessary,  is  devoted  to  explaining  and  illustrating  typical 
examples  of  the  work  to  be  executed  in  the  particular  material  under 
notice.  Thus  the  book  forms  a complete  guide  to  all  the  ordinary 
mechanical  operations  ; and  whilst  professional  workmen  will  find  in  it 
many  suggestions  as  to  the  direction  in  which  improvements  should  be 
aimed  at,  amateur  readers  will  be  glad  to  avail  themselves  of  the  simple 
directions  and  ingenious  devices  by  which  they  can  in  a great  degree 
overcome  the  disadvantage  of  a lack  of  manipulative  skill. 


Price  $2.50  postpaid. 


3 


2 


S PONS’  MECHANICS’  OWN  BOOK. 


CONTENTS. 

Mechanical  Drawing:  buying  and  keeping  instruments;  draw- 
ing boards;  scales;  squares;  paper;  mounting;  mounting  on  linen;  pencil- 
ling; erasing  errors;  inking;  testing  straight-edge;  using  parallel  rules; 
using  compasses;  tints,  dimensions,  and  centre  lines;  title;  nature  of 
drawings;  finishing  a drawing,  colours;  shading;  colouring  tracings;  re^ 
moving  drawings  from  the  board;  mounting  engravings;  fixing  pencil 
drawings;  tracing-paper;  transfer-paper;  copying  drawings  pages  1-13 

Casting’  and  Founding  : general  outline  of  the  operations.  Brass 
and  Bronze  Casting:  characters  of  the  various  alloys  employed,  reactions 
of  the  metals  on  each  other,  mixing  the  metals,  effects  of  tempering;  fur- 
naces, their  construction,  means  of  producing  draught,  fuel,  the  ordinary 
cupola,  the  ordinary  melting  furnace,  the  circular  melting  furnace,  the 
reverberatory  furnace;  crucibles;  moulding;  facing  the  moulds,  filling  the 
moulds,  moulding  in  wax, /onnu  perdrdu  method,  castings  of  natural  ob- 
jects; casting,  pouring  the  metal,  temperature  for  pouring,  escape  of 
gases  from  the  mould,  ornaments  in  relief;  cores;  making  bronze  figures; 
using  plaster  patterns,  finishing  the  casting;  bronzing  its  surface, 
Japanese  bronzes,  inlajung  on  bronzes:  casting  en  cire  perdue,  the  model, 
reproduction  in  wax,  formation  of  the  core,  constructing  the  lanthorn,  re- 
touching the  wax  bust,  preparing  the  bust  before  making  the  cope,  for- 
mation of  the  cope,  firing  the  block,  the  final  casting  in  bronze.  Iron 
Founding:  pattern-making,  cores,  shrinkage,  taper;  tools,  crucibles,  pots, 
moulding  flasks,  packing  the  flasks,  clamping  them;  casting  in  sand, 
with  and  without  cores,  casting  in  loam,  forms  of  castings;  examining 
castings  as  to  quality  and  soundness;  shrinkage  of  iron  castings;  chilling 
iron  castings.  ..  13-44 

Forging’  and  Finishing  : definition  of  the  terms;  explanation  of 

the  technical  phrases,  to  make  up  a stock,  fireirons,  rod,  bar,  plate,  to  take 
a heat,  to  finish  at  one  heat,  to  draw  down,  to  draw  away,  to  upset,  scarf- 
ing, butt-weld,  tongue-joint,  to  punch,  to  drift  out,  the  hammerman,  the 
tuyere  or  tweer;  forges  or  liearths;  anvils;  vices  and  tongs;  hammers;  cut- 
ting tools,  principles  and  practices  in  making  chisels;  drilling  and  boring, 
construction  of  drills;  swaging  tools;  surfacing  tools,  fillingup,  cleaning 
clogged  files,  polishing;  screw  cutting  tools;  forging:  welding,  wrought 
iron,  steel  to  wrought  iron;  tempering,  hardening,  softening,  annealing,  the 
colour  scale,  case-hardening;  examples  of  smiths’  work, — making  keys, 
bolts,  nuts,  tongs,  hammers,  chisels,  files,  scrapers,  di-ifts,  punches, 
spinners,  wrenches;  red-lead  joints;  rust  joints;  riveting  ..  ..  44-90 

Soldering’ : solders,  composition  and  chai-acters  of  these  alloys; 
colouring  solders  to  match  metals.  Burning  or  Autogenous  soldering: 
adaptations  of  the  process,  application  to  pewter,  brass  castings,  iron 
castings,  stove  plate;  burning  seams  in  lead;  the  burning  machine,  air- 
vessels,  bellows,  tubes,  jets,  wind  guards.  Cold  soldering:  the  flux,  the 
solder,  application.  Hard  soldering  various  metals  and  objects.  Soft 
soldering:  the  solders,  fluxes,  irons,  and  bits  employed,  and  precautions 


4 


SPONS’  MECHANICS’  OWN  BOOK. 


3 


needed.  Generalities, — including  blowpipes,  lami3s,  mechanical  blowers, 
supports,  tools,  braziers’  hearth,  means  of  heating  the  iron;  hints  on 
fluxes,  spelter,  commercial  grades  of  solder,  cleaning  impure  solder, 
soldering  zinc  and  galvanized  iron,  soldering  without  an  iron,  soldering- 
brass  to  platinum,  soldering  brass  to  steel,  soldering  iron  and  steel, 
soldering  silver,  soldering  platinum  and  gold,  mending  tin  saucepans, 
soldering  pewters  and  comiio  pipes,  laying  sheet  lead,  mending  leaden 
pipe,  blowpipe  brazing  ..  ..  ..  ..  ..  ..  ..  90-116 

Sheet-metal  working:  Striking  out  the  patterns.  Tools, — mallet, 

cutting,  flattening,  folding,  and  forming  tools.  Working  the  metals, — 
seamless  goods,  bending,  spinning;  seamed  goods,  pipes,  cups,  square 

boxes,  riveting  116-126 

Carpentry ; ITbods;  acacia,  alder,  apple,  ash,  beeches,  birches, 
blackwood,  boxes,  cedars,  cedar  boom,  cheny,  chestnut,  cyjiress,  cypress 
pine,  dark  yellow-wood,  deal,  dogwoods,  ebony,  elms,  eucalyiitus,  fir, 
greenhart,  gums,  hickories,  ironbark,  ironwood,  larches,  lignum-vitas, 
locust-tree,  mahoganies,  mango,  maple,  muskwood,  oaks,  pear,  persim- 
mon, pines,  plane,  poplar,  rosewood,  satinwood,  she-pine,  sneezewood, 
spruces,  stringy-bark,  sycamore,  Tasmanian  myrtle,  teak,  tulip,  walniits, 
willow,  yellow -wood,  yew;  British  Guiana  woods;  Cape,  Natal,  and  Trans- 
vaal woods;  Ceylon  woods;  English  woods;  Indian  woods;  New  Zealand 
woods,  Queensland  woods;  Straits  Settlements  woods;  Tasmanian  woods; 
West  Indian  woods;  growth  of  wood;  felling;  squaring;  defects;  selecting; 
classification;  market  forms;  seasoning;  decay;  preserving;  fireproofing; 
shrinkage;  composition;  strength;  measuring.  Tools:  Guiding  tools, — 
chalk  line,  rule,  straight-edge,  squares,  levels,  bevels,  mitre-box,  com- 
passes, callipers,  shooting-board;  Holding  tools, — pincers,  vices,  clamps; 
Rasping  tools, — saws  (principles,  qualities,  selecting,  using,  filing,  setting, 
sharpening,  gumming;  examples  of  teeth  for  cross-cuts,  back-saws,  buck- 
saws, rip-saws,  circular  saws,  band-saws,  jig-saws,  table  for  jig  and  cir- 
cular saws,  home-made  fret-saw);  files;  Edge-tools, — chisels  and  gouges, 
spokeshaves,  x^lanes,  sliaiqiening  methods  (grindstones,  oilstones),  mis- 
cellaneous forms  (circular  i^lane,  rounder,  box  scraj)er,  veneer  scraper, 
mitre-plane,  combination  fibsters,  adjustable  dado);  Boring  tools, — awls, 
gimlets,  augers,  bits  and  braces,  drills,  (angular  bit  stock,  countersink, 
expansion  bit,  boring  machine) ; Striking  tools, — hammers,  mallets;  Chop- 
ping tools, — axes  and  hatches,  adzes;  Accessories, —bench,  bench-sto]3s, 
holdfasts,  sawing  rest,  bench-vices;  nails,  nail-iDuncli,  nail-jiuller;  screws, 
screw-driver.  Care  of  Tools:  wooden  parts,  iron  parts,  rust  j^reventives, 
rust  removers.  Construction:  joints,  princqiles  of  joints,  equal  bearing, 
close  jointing,  strains,  classification  of  fastenings,  lengthening  joints, 
strengthening  joints,  bearing  joints,  jiost  and  beam  joints,  strut  joints, 
miscellaneous  joints,  keying,  corner-ijiecing,  mortising  and  tenoning, 
half-lap  joint,  dovetailing,  blind  dovetails,  mechanical  aids  in  dovetailing, 
do  welling,  joining  thin  woods,  glueing,  hinging.  Examples  of  Construction: 
workshoji  ai'»j)liances, — tool-chest,  caipenters’  bench,  grindstone  mount; 
rough  furniture,— steals,  ladders,  cask-cradle,  tables,  seats  (box  stool, 
3-legged  stool,  chairs),  washstand,  bedstead,  chest  of  drawers,  dresser, 
garden  and  yard  accessories, — wheelbarrow,  jioultry  and  jiigeon  houses: 
hives,  forcing  frames,  greenhouses,  summerhouses,  fences,  gates;  house 

building, — floors,  roofs,  doors,  windows  126-350 

Cabinet-Making-:  Woods:  apjile,  ash,  beech,  beefwood,  birch, 
box,  canqihor,  canary,  cedar,  cherry,  ebony,  holly,  lime,  locust-wood. 


4 


SPONS’  MECHANICS’  OWN  BOOK. 


mahogany,  maple,  oak,  partridge-wood,  pear,  pine,  plane,  rose,  sandal, 
satin,  teak,  tulip,  walnut,  zebra.  Tools:  tool-chest,  bench,  planes,  sawing 
rest,  moulding  board,  mitring  and  shooting  board.  Veneering:  cutting 
veneers,  fixing  the  veneer;  inlaying,  imitation  inlaying.  Examples:  couch, 
chairs,  folding  bookcase,  chest  of  drawers,  wardrobe,  sideboard  350-386 
Carving  and  FreWork : Carving:  woods, — camphor,  ebony,  lime, 
mahogany,  oak,  pear,  sandal,  sycamore,  walnut,  wild  cherry,  yew;  qualities 
of  wood,  staining,  adaptability;  tools.  Fretwork:  woods;  tools  386-399 
XTpliolstery  ; tools;  leather  work, — small  chair  buttoned  and  welted, 
easy  chairs,  settees  and  couches;  hair  cloth;  fancy  coverings, — plain  seats, 
buttoned  seats,  spring  edges,  needlework  chairs;  mattresses, — spring, 

tufted  top,  folding,  stuffed;  beds  and  pillows  399-405 

Painting,  Graining,  and  Marbling : Painting:  definition  of 
paints;  basic  pigments, — white-lead,  red-lead,  zinc  oxide,  iron  oxide; 
colouring  pigments,— blacks,  blues,  browns,  greens,  lakes,  oranges,  reds, 
yellows;  mediums, — linseed-oil;  driers;  grinding;  storing;  priming;  filling, 
coats;  brushes;  surface;  removing  old  paint;  cleaning  paint;  knotting; 
water-colours;  discoloration;  miscellaneous  paints, — cement  paint  for  car- 
ton-pierre,  copper  paint,  fioor  painting,  gold  paint,  iron  paint,  lead  paints, 
lime  paints,  silicated  paint,  tin-roofing  paint,  transparent  paint,  window 
paint,  zinc  painting;  composition  of  paints;  measuring  painters’  work; 
painters’  cream ; wall  painting,  frescoes,  spirit  fresco,  preparing  the  ground, 
the  pigments  admissible  for  colouring,  preparation  of  the  colours,  produc- 
tion of  delicate  tints,  the  fixing  medium.  Graining:  colours,  tools;  styles 
of  graining — ash,  chestnut,  mahogany,  maple,  oak  (light  and  dark),  rose- 
wood, satinwood,  walnut;  hints.  Marbling:  the  production  of  painted 
surfaces  in  imitation  of  black  and  gold,  black  Bardilla,  Derbyshire  spar, 
dove,  Egyptian  green,  granites,  Italian  jasper,  royal  red,  St  Ann’s,  sienna, 

and  verd  antique  marbles  ..  - 405-433 

Staining  : objects  to  be  attained,  essential  features  to  be  observed; 
recipes  for  black  stains,  black-board  washes,  blue  -stains,  brown  stains, 
ebonizing,  floor  staining,  green  stains,  gray  stains,  imitating  and  darken- 
ing mahogany,  oak  stains,  purple  stains,  red  stains,  imitating  satinwood, 
violet  stains,  imitating  and  darkening  walnut,  and  yellow  stains  433-446 
Gilding:  the  process;  leaf  metals;  composition  and  characters  of  the 
sizes  used  for  attaching  the  leaf;  tools  and  apparatus.  The  operation  of 
Dead  gilding, — preparing  the  surface,  transferring  the  leaf  to  the  surface, 
when  to  lay  it,  making  good  the  blank  spaces,  completing  the  adhesion, 
sizing  the  surface;  modifications  for  dead  gilding  on  plain  wood,  polished 
wood,  cards,  textiles,  painted  and  japanned  surfaces,  metals,  masonry, 
ivory,  and  plaster  of  Paris.  Bright  Gilding — on  transparent  and  opaque 
material,  securing  adhesion  of  the  leaf,  making  fancy  patterns  446-449 
Polishing:  principles.  Marble  polishing:  producing  a plane  sur- 
face, taking  oft’  the  rough,  polishing  up,  rendering  brilliant,  filling  flaws; 
polishing  imitation  marbles.  Metal  polishing:  polishing  metallic  surfaces 
by  hand,  best  means  of  conducting  the  operation,  running  work  in  the 
lathe,  relative  merits  of  oils  and  water;  Belgian  burnishing  powder;  brass- 
polishes;  burnishing,  kinds  of  burnishers,  precautions  in  using  the  burn- 
isher; variations  in  the  tools  and  methods  adapted  for  plated  goods,  gold 
and  silver  leaf  on  wood,  gold  leaf  on  metal;  leather  gilding;  engravers’ 
burnishers;  clockmakers’  iDurnishers;  burnishing  book  e%es,  cutlery,  pew- 
ter, and  silver;  making  crocus;  emery  paper,  emery  paper  pulp,  emery 
wheels;  friction  polish;  german  silver  polish;  glaze  wheels  for  finishing 


6 


St»ONS’  MECHANICS’  OWN  BOOK. 


Bteel;  polishing  gold  and  silver  lace;  polishing  and  burnishing  iron  and 
steel;  plate  powders:  prepared  chalk;  putty  powder;  razor  pastes;  rotten- 
stone  or  tripoli;  rouges.  Wood  polishing:  what  it  consists  in,  the  prelim- 
inary filling  in,  smoothing  the  surface,  rubbing  in  linseed-oil,  the  founda- 
tion coat  of  polish,  the  bodying-in  process,  allowing  to  harden,  putting  on 
the  final  polish,  original  recipe  for  making  the  finishing  polish;  general 
method  of  wood  polishing  adopted  in  America;  the  processes  carried  on  in 
first-class  piano  factories;  collection  of  recipes  for  furniture  creams, 
French  polishes,  reviving  fluids,  compounds  for  darkening  furniture, 
wood-fillers,  and  mixtures  for  black  woodwork,  carvings,  antique  furniture, 
fancy  woods,  black  and  gold  work,  white  and  gold  work,  etc. ; polishing 
woods  in  the  lathe,  modifications  to  suit  hard  and  soft  woods  M9-472 
Varnishing’ ; nature  of  varnishes,  points  governing  their  qualities, 
ingredients  of  varnishes;  the  principal  resins  and  gums,  their  varnish- 
making qualifications;  solvents  and  their  suitability;  driers  and  the  ob- 
jections to  them;  kinds  of  varnish  and  their  essential  differences;  mixing 
varnishes,  white  oil  varnishes  or  spirit  and  turpentine  varnishes;  rules 
regulating  the  application  of  varnishes;  recipes  for  compounding  oil  var- 
nishes (copal,  amber,  Coburg,  wainscot,  etc.),  turpentine  varnishes, 

Brunswick  black,  and  varnish  for  ironwork  472-475 

Mechanical  Movements  : simple,  compound,  and  perpetual  mo- 
tion; pulleys,  blocks  and  tackle,  mangle-wheel  and  pinion,  fusee-chain  and 
spring-box,  frictional  clutch-box,  throwing  in  and  out  of  gear  the  speed 
motion  in  lathes,  tilt-hammer  motion,  ore-stamper  motion,  reciprocating 
rotary  motion,  continuous  rotary  motion  converted  into  intermittent  rotary 
motion,  self-reversing  motion,  eccentrics,  crank  motions,  cams,  irregular 
vibrating  motion,  feed-motion  of  drilling  machine,  quick  return  crank 
motion  of  shaping  machines,  rectilinear  motion  of  horizontal  bar,  screw 
bolt  and  nut,  uniform  reciprocating  rectilinear  motion,  screw  stamping 
press,  screw-cutting  and  slide-lathe  motion,  spooling-frame  motion,  micro- 
meter screw,  Persian  drill,  rack  and  pinion,  cam  between  friction  rollers 
in  a yoke,  double  rack,  substitute  for  crank,  doubling  length  of  stroke  of 
piston-rod,  feed-motion  of  planing  machines,  fiddle  drill,  bell-crank  lever, 
motion  used  in  air-pumps,  shears  for  cutting  met,al  plates,  lazy  tongs, 
toothed  sectors,  drum,  triangular  eccentric,  cam  and  rod,  expansion 
eccentric,  rack  and  frame,  band-saw,  toggle-joint  for  punching  machine, 
silk  spooling  motion,  yoke-bar,  steam-engine  governor,  valve  motion, 
ellipsograph,  elbow-lever,  pawl  and  elbow-lever,  treadle  and  disc,  water- 
wheel governor,  knee-lever;  spiral  grooved  drum;  valve  motion  and  revers- 
ing gear,  obtaining  egg-shaped  elliptical  motion,  carpenters’  bench  clamp, 
uncoupling  engines,  varying  speed  of  slide  in  shaping  machines,  reversing 
gear  for  single  engine,  diagonal  catch  and  hand-gear,  disengaging  eccen- 
tric-rod, driving  feed-rolls,  mangle-wheel  and  pinions,  mangle-rack,  roll- 
ing contact,  wheel  and  pinion,  ratchet-wheel,  worm-wheel,  pin-wheel 
and  slotted  pinion,  Geneva  stop,  stopsj  for  watches,  cog-wheels,  roller 
motion  in  wool  combing  machines,  drag-link  motion,  expanding  pulley, 
chain  and  chain  pulley,  lantern-wheel  stops,  tappet-arm  and  ratchet- 
wheel,  spur-gear  stops,  brake  for  cranes,  dynamometer,  pantograph,  union 
coupling,  anti-friction  bearing,  releasing  sounding-weight,  releasing  hook 
in  pile-giving,  centrifugal  check-hooks,  differential  movement,  combina- 
tion movement,  series  of  changes  of  velocity  and  direction,  variable  motion, 
circular  into  reciprocating  motion,  Colt’s  revolver  movement,  Otis’s  safety 
stop,  Clayton’s  sliding  journal  box,  Pickering’s  governor,  windlass,  rack 


7 


SPONS'  MECHANICS’  OWN  BOOK. 


and  pinion  for  small  air-pumps,  feeding  sawing  macbine,  movable  head 
of  turning  lathe,  toe  and  lifter,  conical  pendulum,  mercurial  compensation 
pendulum,  maintaining  power  in  going  barrel,  parallel  rulers^  Cartwright’s 
parallel  motion,  piston-rods,  gyroscope,  gyroscope  governor,  drilling 
apparatus,  see-saws,  spiral  line  on  cylinder,  cycloidal  surfaces,  polishing 
mirrors,  edge-runners,  portable  cramp  drills,  tread-wheels,  pendulum 
saws,  adjustable  stand  for  mirrors,  cloth-dressing  machine,  folding  ladder, 
lifting  jack,  jig-saw,  polishing  lenses,  four-way  cock,  continuous  circular 
into  intermittent  rectilinear  reciprocating  motion,  repairing  chains, 
Wilson’s  4-motion  feed  for  sewing-machines,  describing  parabolas,  cyclo- 
graphs, describing  pointed  arches,  centrolinead,  proportional  compasses, 
Buchanan  and  Kighter’s  slide-valve  motion,  trunk-engine,  oscillating  pis- 
ton engine,  Boot’s  double  quadrant  engine,  rotary  engines,  bisecting 
gauge,  self-recording  level,  assisting  crank  of  treadle  motion  over  dead 
centres,  continuous  circular  into  rocking  motion.  Boot’s  reciprocating  en- 
gine, Jonval  turbine,  reciprocating  motion  from  continuous  fall  of  water, 
water-wheels,  Fourneyron  turbine.  Barker  mill,  tumbler,  water-raising 
machines,  Montgolfier's  hydraulic  ram,  swing  boat,  lift-pump,  force- 
pump,  rotary  pumps.  Hero’s  fountain,  counter-balance  bucket,  pulley 
and  bucket,  reciprocating  lift,  Lansdell’s  steam  siphon  pump,  swinging 
gutters,  chain  pumps,  steam  hammer,  Hotchkiss’s  atmospheric  hammer, 
rotary  motion  from  different  temperatures  in  two  bodies  of  water,  flexible 
water  main,  air-pump,  aeolipile  or  Hero’s  steam  toy,  Brear’s  bilge  ejector, 
gasometer,  common  windmill,  vertical  windmill,  paddle-wheel,  screw  pro- 
peller, Brown  and  Level’s  boat  detaching-hook,  steering  apparatus, 
capstan,  tongs  for  lifting  stones,  fan  blower,  siphon  pressure  guage, 
mercurial  barometer,  epicyclic  trains,  aneroid  or  Bourdon  gauge;  gearings, 
brush  wheels,  friction  wheels,  sun-and-planet  motion,  mangle  or  star 
wheel,  jumping  rotary  motion,  registering  revolutions,  mangle-rack, 

wheel-work  in  base  of  capstan  . . 475-531 

Turning- : the  operation.  Lathes,  mandrels,  chucks,  poppet-heads, 
rests,  supports,  boring  collars,  true  frames,  self-acting  slide-rest,  complete 
double-gear  foot-lathe,  single-gear  foot-lathe,  compound  slide-rests;  form 
of  tools,  shape  of  cutting  edges,  angle  of  holding,  screw  cutting,  skilful- 
ness with  hand  tools.  Tools:  their  selection.  Metal-turning  tools : their 
temper,  grinding,  cutting  angles;  iron -turning  tools:  common  roughing 
tool,  round  nose,  parting  tool,  knife  tool  for  finishing  edges  and  faces, 
boring  tools  for  hollow  cylinders,  square  nose,  scraping  tool,  spring  tool, 
finishing  tools  for  rounded  work;  brass-turning  tools;  adapting  tools; 
making  a grindstone;  whetting  tools;  making  milling  tools  for  screw-heads; 
making  centre  punches  and  drills;  scribing  block.  Tool-holders:  the 
swivel  tool-holder  and  its  adaptation  to  various  needs — e.g.  planing  under 
horizontal  surface  of  a lathe-bed,  planing  in  a limited  space,  clearing  a 
projecting  boss,  cutting  a vertical  slot,  undercutting  slots  and  clearance 
corners,  cutting  square  threads;  grinding  the  cutting  edges,  angle-gauges 
for  maintaining  correct  forms;  rehardening  cutters.  Drilling  and  boring 
tools;  experiments  on  the  cutting  angle;  why  common  drills  run;  the 
grinding  line;  grinding  machines  for  twist  drills.  Milling:  range  of  mil- 
ling machines;  modern  milling  cutters — how  they  are  made  and  set;  vari- 
ous forms, —disc,  cylindrical,  circular  saw-like,  conical,  annular,  and 
complex  forms;  cutting  speed  and  power  required.  Wood-turning  tools; 
plain  gouges  and  chisels;  turning  straight  stuff;  holding  the  tool;  flaws  in 
tools;  selection  of  gouges  and  chisels  ..  ..  , ..  531-561 


S 


SPONS’  MECHANICS’  OWN  BOOK. 


7 


Masonry  \ Stoneioork:  durability  of  natural  stone,  physical  struct- 
ure and  its  influence;  working;  hardness;  strength;  weight;  appearance; 
position  in  quarry;  seasoning;  natural  beds;  destructive  agents, — chemical, 
mechanical,  lichens,  molluscs;  quarrying;;  granite;  serpentine;  sandstones; 
limestones; — marble,  compact  limestones,  shelly  limestones,  magnesian 
limestones,  preserving, — painting,  silicatising,  other  processes;  stone- 
masons’ tools, — saws,  mallets,  chisels;  laying  stonework, — rough  rubble, 
course  rubble,  combined  rubbles,  ashlar  work;  joining  stones;  stone  walls. 
Brickwork:  bricks,— classification,  cutters,  rubbers,  ordinary  building, 
underburnt;  qualities  of  a good  building  brick;  size;  testing.  Terracotta 
blocks,  joining  them,  their  advantages  and  disadvantages.  Limes:  rich  or 
fat  limes,  poor  limes,  hydraulic  limes.  Sand:  argillaceous,  siliceous,  and 
calcareous,  its  characters  and  impurities;  washing,  substitutes.  Mortar: 
its  quality  governed  by  that  of  its  constituents;  danger  of  using  fat  limes; 
superiority  of  hydraulic  lime  and  cement;  objects  of  using  sand,  and  con- 
ditions to  be  observed;  choice  of  water;  proportions  of  sand  desirable; 
measuring  the  ingredients  of  mortar;  mixing  the  mortar;  selenitic  mor- 
tar; lime  and  cement  mixtures;  grout;  moisture  essential  to  the  setting  of 
mortars.  Bricklayers’  tools.  Laying  bricks:  sizes,  breaking  joint,  bond; 
headers,  stretchers,  and  closers; English  and  Flemish  bond;  raking  courses 
in  thick  walls;  keeping  the  work  level  and  plumb;  ensuring  adhesion 
between  the  brick  and  the  mortar;  pointing  and  finishing  brickwork, — 
striking,,  tuck  pointing,  weather  joint,  bastard  tuck,  bastard-tuck  pointing, 
evils  and  uselessness  of  the  common  methods  and  description  of  how  it 
should  be  done;  examples  of  first  and  second  course  of  walls  in  various 
styles  of  bond;  hollow  walls;  fireplaces.  Concrete:  the  materials  compos- 
ing it,  their  choice  and  proportions;  mixing;  laying  moulds  for  construct- 
ing walls;  the  cementing  material;  bulk  produced;  selenitic  concrete; 
expansion  of  concrete.  Saltpetreing  of  walls — causes  and  cure.  Damp 
walls  and  their  prevention.  Scaffolding  for  bricklayers  . . 561-604 

Plastering*  and  Whitewashing’ : Plastering:  materials, — basis  of 
plasters,  Portland  cement,  Parian  or  Keating’s  cement,  composition  of 
the  several  coats;  lime,  water,  and  hair  used;  coarse  stuff,' fine  stuff,  plas- 
terers’ putty,  gauged  stuff;  selenitic  plaster;  rough  cast;  stucco;  Marezzo 
marble;  mouldings  and  ornaments  in  plaster  and  papier  mache;  tools; 
lathing;  laying  and  pricking-up.  Whitewashing,  Calcimining  or  Distemper 
Painting:  common  whitewash  or  lime  whiting;  common  colouring,  making 
whiting;  white  and  coloured  distemper;  indoor  operations  on  good  ceilings; 
a simple  lime-wash ; a good  stone-colour  wash ; a waterproof  calcimine  that 
bears  washing;  re -whiting  an  old  dirty  ceiling;  further  hints  and  recipes 

for  milk  distempers  and  whitewashes  604-613 

Roofing : pitches  of  roofs;  thatching;  shingles  or  shides;  felt;  Willes- 
den  paper;  slates;  tiles;  metallic  roofing  ..  ..  ..  ..  613-627 

Glazing:  Glass  of  various  kinds;  putty,  to  soften  putty;  tools; 
lead  glazing;  special  methods  of  glazing  not  dependent  on  putty  627-634 
Bell-hanging  : the  ordinary  domestic  bell  system,  tubes,  wires, 
cranks,  gimlet,  bells,  and  general  directions;  electric  bells, — the  battery, 
wires,  circuit-closer,  bells,  arrangement  of  series;  systems  with  1 bell  and 
1 press  button,  1 bell  and  2 buttons,  2 bells  and  1 button,  annunciator 
system,  double  system,  bell  and  telephone;  making  electric  bell, — back- 
board  and  cover,  electro-magnet,  bobbins  or  coils,  filling  the  bobbins 

with  wire,  putting  the  bell  together  634-640 

Gas-fitting  : fixing  brackets  and  pendants,  using  the  tongs  640-642 


9 


SPONS’  MECHANICS’  OWN  BOOK. 


Paper-hanging : classification  of  wall  papers,  their  characters  and 
uses;  colours  to  avoid;  papers  for  damp  walls;  varnishing,  sizing,  painting 
and  washing  wall  papers;  wall  papers  considered  as  ornament,  and  rules 
as  to  colour,  pattern,  dado,  and  frieze;  pasting,  cutting,  and  hanging  the 
paper,  and  precautions  to  be  observed  ..  ..  ..  ..  642-646 

Lighting : natural  lighting,  window  area;  artificial  lighting  by  can- 
dles, oils,  gas,  and  electricity.  Oil  lamps,  their  principles,  and  the  objects 
aimed  at  in  the  various  forms  -of  wick,  burner,  and  regulator.  Gas,  how 
supplied,  computing  the  number  of  burners  necessary,  advantage  of  a 
ventilator;  how  to  turn  off  gas  at  night;  construction  of  burners  and  con- 
ditions that  govern  it;  distribution  of  jets;  selection  of  glass  globes;  how 
to  utilize  fully  the  luminosity  of  the  gas.  Electric  lighting, — rules  and 
regulations  for  minimizing  risk,  joining  the  wires  ..  ..  '646-654 

Ventilating  : window  ventilators,  Butler’s  system,  Arnott’s  system, 
Morse’s  system,  American  plan  in  large  buildings,  method  at  St.  Thomas’s 
Hospital,  method  at  Guy’s  Hospital,  Harding’s  ventilators,  system  adopted 
by  the  Sanitary  Engineering  and  Ventilating  Co.,  Boyle’s  air-pump  venti- 
lators, Kershaw’s  chimney  cowl  654-658 

"Warming:  conserving  heat,  double  windows; radiant  heat  and  hot 
air,  their  relative  position  as  regards  health;  open  grates;  open  stoves, 
economizing  fuel  with  ordinary  grates;  close  stoves;  hot-air  furnaces;  hot- 

water  heating;  steam  heating  658-667 

Foundations  : points  to  be  considered ; foundations  on  rock,  gravel, 
sand,  clay,  firm  ground  overlying  soft  ground,  soft  ground  of  indefinite 
thickness;  concrete;  fascines;  piling;  footings;  damp  course  ..  667-670 

Roads  and  Bridges  : Boads:  the  original  foot  tract,  temporary  roads 
in  unmapped  country,  one  made  across  the  Chenab;  plank  roads  and 
turnouts;  pavements, — flagging,  asphalt, ^cement  floors.  Bridges:  simple 
timber  bridge,  paved  causeway,  boat  bridges,  travelling  cradles,  rope 

bridges,  weighted  beams  670-676 

Banks,  Hedges,  Ditches,  and  Drains  676-677 

Water  Supply  and  Sanitation:  river  water,  cleansing;  spring 
water,  filtering;  wells,  sinking  in  various  strata,  steining,  simple  plan  used 
in  India;  pumps  and  various  other  methods  of  raising  water;  ponds,  cavern 

tanks,  artificial  rain  ponds.  Drains  and  traps  677-680 

House  Construction : Log  huts,  building  the  fireplace.  Frame 
houses.  Earth  walls.  Stairs.  Colonial  houses, — peculiar  conditions  of  build- 
ing in  Canada,  Ceylon,  and  India,  to  suit  the  climatic  requirements  680-688 


SPON  & CHAMBERLAIN, 

PUBLISHERS,  IMPORTERS  AND  BOOKSELLERS, 

)2  CORTLANDT  STREET,  NEW  YORK. 


10 


2g  PLATBS,  5 K in.  X 8 in.  PRICE  50  CEXTSe 


A 

SYSTEM 

OF 

EASY  LETTERING. 

BY 

J.  HOWARD  CROMWELL. 

ATJTHOB  OF  “A  TEEATISE  ON  TOOTHED  GEABING,”  "A  TKEATISE  ON  BKI.TS  AND  PULIiETS.” 


This  useful  -work  gives  twenty-six  different  forms  of  alphabets,  all 
constructed  on  the  same  general  system.  The  space  to  be  lettered  is  to 
be  divided  into  parallelograms  or  squares,  as  the  case  may  be,  and  within 
these  as  a guide  the  different  letters  are  drawn  and  inked.  The  guide 
squares,  which  have  been  made  in  pencil,  are  then  erased,  leaving  the 
final  letters.  On  so  simple  a basis  as  this  quite  a variety  of  effects  are 
produced  in  flat  and  block  letters.  Scientific  American. 

This  little  book  will  be  appreciated  by  draftsmen  who  wish  to  use 
plain  letters  (and  yet  somewhat  different  from  the  ordinary  run  of  letters) 
for  the  titles  on  drawings.  The  book  vdll  also  be  valuable  and  useful  to 
any  one  who  has  had  no  practice  in  lettering,  as  the  easy  method  given 
for  forming  the  letters  will  enable  a person  to  form  the  letters  correctly, 
and  with  a little  practice  to  do  so  quickly.  Amen'ican  Machinist. 

Mr.  Cromwell  has  done  a good  work  in  getting  out  this  little  book, 
providing  a system  of  lettering  which  is  both  neat  and  easy  of  execution. 
Instead  of  giving  the  conventional  series  of  ornamental  letters,  many  of 
which  take  more  time  than  the  drawing  is  worth,  we  have  here  several 
alphabets  which  give  sufficient  variety  for  all  ordinary  purposes,  and  yet 
are  so  simple  as  to  be  within  the  range  of  ability  of  the  freshest  ap- 
prentice. "We  recommend  the  book  to  every  draftsman.  Mechanics. 

After  forty  years  experience  in  mechanical  and  architectural  drawing 
in  this  and  other  countries,  we  consider  this  among  the  best,  most 
practical  and  useful  books  that  treat  on  lettering  for  ordinary"  practical 
purposes.  Master  Steam  Fitter. 

Designs  are  given  in  great  variety,  and  the  lines  of  projection  given 
with  them  enables  any  one  to  enlarge  or  reduce  with  great  ease  and  exact- 
ness. Manufacturers  Gazette. 


II 


12 


Books  for  Architects. 


Hngflisll  Arcliitecture,— The  Seven  Periods  of  English 
Architecture,  defined  and  illustrated.  By  Edmund  Sharpe,  M.A. 
Contents  of  Chapters  ; i. — Introduction.  2. — Classification.  3. — 
Compartments.  4. — Saxon  Period.  5. —Norman  Period.  6. — Transi- 
tional Period.  7. — Lancet  Period.  8. — Geometrical  Period.  9. — 

Curvilinear  Period.  10. — Rectilinear  Period.  With  20  full-page 
steel  engravings  and  wood  cuts.  8vo.,  cloth.  $5.00. 

Plan  and  Map  Drawing:.— The  Draughtman’s  Handbook 
of  Plan  and  Map  Drawing.  Including  Instructions  for  the  Prepara- 
tion of  Engineering,  Architectutal  and  Mechanical  Drawing.  By 
Geo.  Andre,  C.E.  Contents. — Part  i. — The  Essential  Elements. 
The  Drawing  Office  and  its  Furnishings.  Geometrical  Problems. 
Lines,  Dots  and  their  Combinations.  Colors.  Shadings  Part  2. 
Applications,  Lettering,  Bordering  and  North  Points.  Scales.  Plot- 
ting. Civil  Engineers  and  Surveyors’  Plans.  Regulations  of  Local 
Government  Board.  Map  Drawing.  Mechanical  and  Architectural 
Drawings.  Copying  and  Reducing.  Trigonometrical  Formulae. 
Inclined  Measure.  Curvature  and  Refraction.  Index.  150  pages. 
86  illustrations,  numerous  tables  and  33  plain  and  colored  plates. 
-|to.,  cloth.  $3-75. 

Scamping  'Trick.S,  and  Odd  Knowledge  Occasionally  Prac- 
tised upon  Public  Works.  Chronicled  from  the  Confessions  of  some 
old  Practitioners.  By  John  Newman.  Contents  : i. — Introduc- 

tion. 2. — Screw  Piles — General  Consideration — Manipulation  for 
“Extra  Profit.*’ — Screw  Piles — Details.  4. — Iron  Piles— Arrange- 
ment Driving — Sinking  by  Water-Jet.  5. — Timber  Piles.  Pile-driv- 
ing—General  Considerations.  6. — Timber  Piles — Manipulation  for 
“ Extra  Profit.”  7. — Masonry  Bridges  . 8. — Tunnels.  9. — Cyl- 
inder Bridge  Piers.  10. — Drain  Pipes — Blasting  and  Powder- 
carriage.  II. — Concrete-Puddle.  12. — Brickwork — Tidal  Warn- 

ings— Pipe  Joints— Dredging.  13. — Permanent  Way.  14. — “Extra” 
Measurements — Toad-stool  Contractors — Testimonials.  15  — Men 
and  Wages — “ Sub,”  from  the  word — A Subcontractor’s  Scout  and 
Free  Traveller.  129  pages,  i2mo.,  cloth.  $1.00* 

Drauglitsmaiisliip.— Hints  on  Architectural  Draughtsman- 
ship. By  G.  W.  Tuxford  Hallatt.  Contents  Introduction. 
Freehand  Drawing.  Plans,  Elevations  and  Sections.  Perspectives, 
Etchings.  Water-color  Perspestives.  Competition  Drawings.  Ar- 
chitecture and  Good  Drawing  Inseparable.  Concluding  Hints. 
80  pages,  i6mo.,  cloth.  60  cts. 

Xlie  Builder’s  Clerk.. — A Guide  to  the  Management  of  a 
Builder’s  Business.  By  T.  Bales.  92  pages,  lomo.,  cloth.  60  cts. 

Xlie  Clerk  of  Works. — A Vade  Mecum  for  all  Engaged 
in  the  Superintendence  of  Building  Operations.  By  G.  G.  Hopkins. 
53  pages,  i6mo.,  cloth.  do  cts 


13 


Architectural  Examnles 


BRICK,  STONE,  WOOD  AND  IRON. 

BY 

WIZZIAM  FXILLEItTON,  Architect. 


A complete  work  on  the  Details  and  Arrangement  of  Building  Construction 
and  Design.  Containing  200  plates  with  numerous  drawings  selected  from  the 
Architecture  of  former  and  present  times.  The  details  and  designs  are  drawn 
to  scale  %-inch,  J^-inch,  y^-mch,  and  full  size  being  chiefly  used.  The  plates 
are  arranged  in  two  parts. 

The  first  part  contains  details  of  work  in  the  four  principal  building  ma- 
terials, the  following  being  a few  of  the  subjects  in  this  part : Various  forms 
of  doors  and  windows, wood  and  iron  roofs,  half-timber  work,  porches,  towers, 
spires,  belfries,  flying  buttresses,  groining,  carving,  church  fittings,  construc- 
tive and  ornamental  iron  work,  classic  and  gothic  molds  and  ornament,  folia- 
tion (natural  and  conventional),  staiiied  glass,  colored  decoration,  a section  to 
scale  of  the  Great  Pyramid,  Grecian  and  Roman  work.  Continental  and  English 
Gothic,  pile  foundations,  chimney  shafts  according  to  the  regulations  of  the 
London  County  Council,  Board  schools. 

The  second  part  consists  of  drawings  of  plans  and  elevations  of  buildings, 
arranged  under  the  following  heads  : Workmen’s  cottages  and  dwellings,  cot- 
tage residences  and  dwelling  houses,  shops,  factories,  warehouses,  schools, 
churches  and  chapels,  public  buildings,  hotels  and  taverns,  and  buildings  of  a 
general  character."”  - 

All  the  plates  are  with  particulars  of  the  work,  with  explan- 

atory notes  and  dimensions  of  the  various  parts. 

The  purpose  of  this  book  is  chiefly  to  serve  as  a condensed  form  of  refer- 
ence for  examples  of  the  most  essential  parts  of  building  construction  and 
ornament,  classified,  but  arranged  somewhat  in  the  nature  of  a sketch-book. 

The  work  is  also  intended  to  be  of  use  to  the  student  and  those  already 
actively  engaged  in  architectural  work,  whether  designing  the  arrangement, 
construction,  and  ornament  of  buildings,  or  engaged  among  the  different  trades 
in  their  execution. 

In  Demy  Do,  handsomely  hound  in  cloth, 

PRICE,  $6.00. 


14 


SECOND  EDITION— REVISED. 


STANDARD 

PRACTICAL  PIOMBIHG. 

BEING 

ol  Complete  Encyclopcedia  for  Practical  Plumbers  and 
Guide  for  Architects,  Builders,  Gas-fitters,  Hot 
Water  Fitters,  Ironmongers,  Lead  Burners, 
Sanitary  Engineers,  Zinc  Worhers,  etc. 


CONTENTS  OF  VOLUME 

Lead  and  its  manipulation.  Lead  and  lead  mines.  Lead,  separa- 
tion of  silver  from.  Lead,  red  and  white.  Lead,  use,  nature,  and 
properties  of.  Workshop  and  its  tools.  Lead  casting  and  tools.  Win 
dow  lead.  Lead  barrel  casting.  Lead  pipe.  Lead  pipe  presses.  Lead 
milling.  Rolling-mills.  Tin  and  its  manipulation.  l\letals  and  alloys. 
Solder.  Sheet  lead  cutting.  Soil  pipes.  Lead  burning.  Joint-making. 
Elbows  and  joints.  Bends.  Traps.  Siphonage  explained.  Brass 
gratings.  Cisterns.  Filters.  Sanitary  plumbing  job  complete.  Ven- 
tilation. Cowls.  Wash-basins,  baths,  hot  water  supply.  Proper  house 
drainage.  Joint-making.  Testing  drains.  Soil  and  rain  water  pipe 
working.  Tacks  and  ears.  Astragals.  Rain  water  pipes.  Soil  pipe 
and  trap  fixing.  Waste  pipe  and  trap  fixing.  Waste  pipes  and  venti- 
lation. Closets.  Urinals.  Closet  water  supply.  Closet  valves.  Closet 
service  boxes  and  valves.  Waste  preventers.  Lead  light,  and  stained 
glass  glazing.  Ornamental  lead  light  glazing.  Stable  drainage. 


355  with  769  illii^trationi^.  Small  4to,  cloth,  $3.00, 


15 


VOL.  2-NOW  READY- 


PRACTICAL  PLUMBING. 

BY  PHILIP  JOHN  DAVIES. 


SYT^OfSIS  OK  COJ^TTEPiJXS. 

Introduction.  Water  Supply. — Wells,  foul  air  in  wells,  well- 
heads, springs,  percolation,  artesian  wells,  well  sinking,  gas  wells, 
well  boring  and  artesian  well  tubes,  well  boring  tools,  windlasses 
and  buckets,  tube  wells  driving  tube  wells.  Pumps. — Free  pumps, 
hand,  chain,  bucket,  jack,  overhand,  floating,  wheel,  hanging, 
plunger  and  lift  pumps.  Atmospheric  pumps.  Beer  pumps  Dia- 
phragm pumps.  Bellows  pumps.  Fire  engine  and  ships’  pumps. 
Repairing  pumps,  Pole  and  plunger  pumps.  Deep  well  pump 
work  and  rigging.  Double  and  triple  lift  pumps.  Working  pumps. 
Horse  driven  pumps.  Wind  pumps.  Puisometer  pumps.  Continuous 
“primed”  pumps.  Air  chamber  section  pumps.  Continuous  action 
lift  and  plunger  pump.  Pump  accessories.  Garden  pumps.  Steam 
pumps,  Turbines.  Water  motors.  Hydraulic  rams.  Water  pres- 
sure tables.  Fountains,  fitting  up  fountains.  Hydraulic  elevators. 
Pipe  and  joint  tester.  Water  analysis.  General  town  water  supply. 
Table  of  the  working  strength  of  cast-iron  pipes,  weights  and  thick- 
nesses. Service  pipes  from  street  mains.  Lead  pipes.  Bursting 
strain  of  lead  pipes.  Brass  work,  ferrules,  stop  ferrules.  Tapping 
mmins.  Tapping  water  mains  under  pressure.  Tools  and  fittings. 
Analysis  of  tin,  lead  and  plumber’s  solder.  Geometry  for  plumbers. 
(This  article  has  been  especially  written  for  this  work  and  is  illus- 
trated with  about  200  diagrams.)  Mechanics  for  plumbers.  Roof 
Work. —Lead  laying.  Gutters,  drips  and  falls.  Hints  for  measur- 
ing lead  gutters.  Dormers,  welts  and  beads.  Bossing  up  corners. 
Flats  and  seam  rolls.  Hips  and  ridges.  Rain  water  pipes.  Louvres 
and  other  ventilators.  Turrets,  spires,  domes,  skylights,  lanterns, 
etc.,  etc.  Stone  channel  gutters,  stone  coping  or  cornice  gutters. 
Ornamental  rain  water  heads.  Finials  and  weather  cocks.  Solder 
dotting.  Hot  Water  Baths,  Heating,  etc. — Sinks,  lavatories,  their 
fittings  and  accessories.  Baths  and  bath  fittings  and  accessories, 
Portable  baths,  hip  baths,  swimming  baths.  Repairing  valves,  cocks, 
etc.  Bath  distributors.  Wash  basins  and  fittings.  Laundry  drying 
rooms.  Feed  cisterns.  Steam  cooking  ranges.  Hydraulic  press 
pipe  joints.  House  heating  by  steam.  Heating  by  hot  water. 
Heating  by  radiators.  Water  boilers.  Heating  water  by  steam 
pipes  (dry  steam).  Heating  water  by  injectors  (wet  steam).  Plumb- 
ers’ tools  for  iron  pipe  work.  Stand  pipes,  fire  plugs,  tanks  and 
cisterns.  Water  meters.  Drinking  fountains.  Sizes  of  furnaces  for 
heating  different  lengths  of  piping.  Warmth  and  dust  by  hot  water 
pipe  heating.  Hot  water  and  steam  thermometers.  Heating  ca- 
pacity. Jointing  pipes.  Examination  questions.  Complete  index. 
802  pages,  296  illustrations,  4to.,  cloth.  $4.50.! 


16 


HOT  WATER  SUPPEY 


A PRACTICAL  TREATISE 

UPON 

THE  FITTING  OF  HOT  WATER  APPARATUS  FOR 

DOMESTIC  AND  GENERAL  PURPOSES. 

BY  F.  DYE. 


Contents. — Boilers.  Cylinders  and  tanks.  Pipes.  Cocks. 
Circulation,  explanation  and  cause.  General  description  of  apparatus. 
The  high  or  old  tank  system.  The  cylinder  system.  Improved 
systems,  etc.  General  directions,  position  of  pipes,  charging  and 
testing,  discolored  water,  etc.  Experimental  glass  apparatus,  results 
noted.  Incrustation  and  causes,  boiler  cleaning,  etc.  Explosions  and 
causes' -'safety  valves,  felting  and  jcacking  pipes,  etc.  Coils  and 
coil  services,  twin  services,  how  to  convert  the  tank  system  into 
tn.c  cylinder  s^’stem,  how  to  lit  a H.P.  boiler  to  lie  used  for  low 
pressure  purposes  at  first.  Estimates  and  estimating,  (English). 
W orkmen’s  tools.  Common  faults.  The  supply  or  ball-valve  cistern, 
-pressure  boilers. 


The  subject  is  treated  iu  a very  clear  aud  simple  manner,  and  yet  many  points 
are  brought  forward  which  will  be  of  service  to  skilled  men.  Boston  Journal  of  Cor.i- 
rnerce. 

As  boo  water  circulation  is  based  upon  certain  definite  scientific  principles,  the 
information  contained  in  this  book  will  be  found  valuable  to  those  who  are  making  a 
study  of  heating  houses  by  hot  water  circulation,  as  well  as  those  who  are  studying 
the  means  of  domestic  supply.  American  Artisan. 

The  author  Mr.  Dye.  has  aimed  to  supply  a book  which  is  so  plainly  written  tliat 
those  who  are  unfaniiliar  with  the  work  may,  without  trouble,  understand  the 
methods  which  he  explains.  This  done,  it  is  perfectly  certain  that  those  who  are 
familiar  with  the  work  by  reason  of  their  mechanical  connection  with  it.  will  under- 
stand the  reasons  he  gives  for  suggesting  certain  methods. 

The  book  seems  the  result  of  an  intelligent  aud  earelul  study  of  the  subject,  ana 
will  be  found  exceedingly  u.seful  by  all  who  have  to  deal  with  hot-water  apxmratus. 
Building. 

Pipages,  imth  25  illustrations,  V2mo,  cloth,  $1.00  postpaid. 


17 


NEW  EDITION,  REVISED  AND  ENLARGED 


A PRACTICAL  TREATISE 

UPON 

Wasming  t 'Buildings 

BY 

HOT  WATER, 

AND  UPON 

Heat  and  Heating  Appliances  in  general,  with  an  inquiry  respect- 
ing ventilation;  the  cause  and  action  of  draughts 
in  chimneys  or  flues,  and  the  laws 
relating  to  combustion. 


By  CHAS.  HOOD,  F.R.S.,  F.R.A.S.,  &c. 

RE-WRITTEN  BY 

FREDERICK  DYE. 


OOITTEITTS- 

pl^EAT.  Circulation  of  water.  Air  in  pipes.  Supply  of  water.  Ex 
pansion  of  pipes.  Irregular  forms  of  apparatus.  Causes  affecting 
circulation  of  water  and  apparatus.  Examples  of  hot  water  apparatus. 
Boilers.  Boilers  for  brick  setting.  Appliances  and  fittings  for  horticultural 
works.  Quantities  for  horticultural  works.  Fuel,  stoking  and  attention  to 
horticultural  works.  Upon  warming  buildings  (low  pressure).  Pipes  and 
appliances  for  building  works.  Quantities.  Examples  of  low  pressure 
apparatus  for  buildings.  High  pressure  apparatus.  Warming  buildings 
by  heated  air.  Hot-water  works  for  baths,  lavatories,  and  other  domestic 
and  general  purposes.  Combustion,  its  application  to  warming  purposes 
by  grates,  etc.  Chimneys.  Ventilation.  Appendix.  Index. 

512  PAGES,  WITH  277  ILLUSTRATIONS,  PRICE,  $6.00. 

i8 


TURKISH  mTH. 

ITS  DESIGN  AND  CONSTRUCTION. 

BY  

ROBERT  OWEN  ALLSOP. 


Contents. — Introduction.  The  general  requirements  of  a public  bath. 
The  general  disposition  of  plan  of  public  baths.  A detailed  consideration 
of  features  peculiar  to  the  bath.  Heating  and  ventilation.  Water-fittings 
and  appliances.  Lighting,  decorating  and  furnishing.  The  Turkish  bath 
in  the  house.  The  bath  in  public  and  private  institutions.  The  Turkish 
bath  for  horses. 

Illustrated  with  twenty-seven  plans  and  sections,  from  scale 
drawings  by  the  author. 

8VO,  CLOTH,  $2.50. 


TKe  ril^DROi>AtHl(  E5TABli5HN|ENT 

flWO  ITS  BATHS, 

By  ROBERT  OWEN  ALLSOP. 

Contents. — General  considerations.  Practical  requirements  of  the 
Hydropathic  establishment.  Some  existing  institutions.  Baths  and  treat- 
ments, and  the  arrangement  of  the  bath  house.  Vapor  baths  and  the 
Russian  bath.  The  douche  room  and  its  appliances.  Massage  and  electri- 
cal treatment.  Pulverisation  and  the  Mont  Dore  cure.  Inhalation  and  the 
pine  cure.  The  sun  bath.  Index. 

Illustrated  with  plans  and  sections. 

8VO,  CLOTH,  $2.00. 


19 


CHARTS  FOR 


Low  Pressure  Steam  Heating 

FOR  THE  USE  OF 

ENGINEERS,  ARCHITECTS,  CONTRACTORS  AND 
STEAM  FITTERS. 

By  J,  H.  KIHEAI.Y,  M.E. 

M.  Am.  Soc.  M.  A".,  M.  Am.  Soc.  of  H.  and  V.  Eng'rs.,  Ssfc. 


The  author  has  long  been  in  the  habit  of  using  charts  to  aid  him 
in  his  work.  Knowing  the  value  of  them  in  saving  time,  simplifying 
work  and  ensuring  correct  calculations  he  feels  confident  that  they 
will  be  appreciated  by  engineers,  architects  and  contractors,  for  whose 
benefit  they  have  been  compiled.  Care  has  been  taken  to  make  the 
charts  as  clear  and  as  easily  understood  and,  above  all,  as  accurate  as 
possible.  They  have  been  based  upon  theoretical  considerations, 
modified  by  what  is  considered  to  be  good  practice  in  this  country. 


Chart  i.— This  chart  is  for  determining  the  number  of  square  feet 
of  heating  surface  of  a low  pressure  steam  heating  system,  pressure 
not  to  exceed  5 lbs.  per  square  inch  by  the  gauge,  necessary  to 
supply  the  heat  lost  through  the  various  kinds  of  wall  surfaces  of 
rooms.  The  chart  is  divided  into  four  parts.  Chart  2. — For  deter- 
mining the  diameters  of  the  supply  and  return  pipes  for  a heating 
system.  Chart  3. — For  finding  the  number  of  square  feet  of  boiler 
heating  surface  and  the  number  of  square  feet  of  grate  surface  for 
a boiler  that  is  to  supply  steam  to  a steam  heating  system.  Chart  4. — 
For  determining  the  area  of  the  cross  section  of  a square  flue,  or  the 
diameter  of  a round  flue,  leading  from  an  indirect  radiation  heater  to 
the  register  in  a room  to  be  heated. 

hull  details  are  given  for  the  use  of  these  cards. 

These  four  charts  are  printed  on  heavy  white  card-board  and  bound 
together  with  cloth,  size  13  in.  by  9^4^  in., 

'[ hese  cards  are.  securely  packed  for  mail  atid  se?il  to  any  part  of 
the  World  on  receipt  of  price. 


20 


Water  Snpply,  Plnmbing,  Drainage, 


Hot  'Water  Supply,  A practical  treatise  upon  the  fitting  of 
hot  water  apparatus  for  domestic  and  general  purposes.  By  F.  Dye. 
82  pages,  25  illustrations,  i2mo,  cloth.  $i  00. 

Hot  Water  Kittingf  and  Steam  Cooking  Apparatus.  A 
guide  for  builders  and  others  for  the  fitting  and  fixing  of  boilers 
and  pipes  for  the  circulation  of  hot  water  for  heating  buildings  and 
for  domestic  purposes,  with  a chapter  on  boilers  and  fittings  for 
steam  cooking.  By  F.  Dye.  92  pages,  23  illustrations,  cloth,  50c. 

Plumbing:,  Hraina^e  and  Water  Supply,  and  Hot 

Water  Fitting.  By  John  Smeaton,  C.  E.  Drainage.  City  wells. 
External  plumbing.  Internal  plumbing  and  fittings.  Tapping  mains 
under  pressure.  Ornamental  lead  work.  Heating.  Hot  water 
work,  etc.,  etc.  236  pages,  217  illustrations,  Svo.,  cloth.  $3.00. 

Treatise  on  Modersi  Sanitary  Appliances  for 

Healthy  Residences  and  Public  Institutions.  By  F.  Colyer,  C.E. 
For  the  use  of  students,  etc.  General  instructions.  Drainage.  In- 
ternal work.  Water  supply.  Heating  apparatus  for  buildings. 
Swimming  baths.  Sundry  sanitary  arrangements  in  the  construc- 
tion of  residences,  cleaning  drains,  etc.  Electric  light  in  residences 
and  public  institutions.  Index,  etc.  118  pages,  i2mo.,  cloth,  \ 2 00.* 

Bad  Brains  and  How  to  Test  them.  With  notes  on  the  ven- 
tilation of  sewers,  drains,  and  sanitary  fittings,  and  the  origin  and 
transmission  of  zymotic  diseases.  By  R.  Harris  Reeves.  68  pages, 
3 plates,  i2mo.,  cloth.  $1.40. 

Public  Batbs  and  Wasbbouses.  By  Robt.  Owen 
Allsop.  Contents  of  Chapters  ; — i.  Introduction.  2.  Schedule  of 
accomodation.  3.  General  arrangement  of  baths  and  washhouses. 
4.  Slipper  baths.  5.  Swimming  baths.  6.  The  public  washhouse. 
7.  The  establishment  laundry.  8.  The  engineer's  department,  q 
Water  supply.  10.  The  heating  of  swimming  baths,  ii.  The  Turkish 
bath  in  public  bathing  establishments.  12.  Baths  for  the  poor. 
Index.  98  pages,  18  illustrations  and  4 folding  plates,  8vo,  cloth,  $2.50. 

Hints  to  House  Hunters  and  'House  Holders.  By 
Ernest  Turner.  Chapter  Headings  : — Househunters  and  House- 
holders. 2.  Requirements.  3.  Situation  and  aspect.  4.  Soil.  5. 
Con.struction.  6 Water  supply.  7,  Drains.  8.  Ventilation  and 
heating.  9.  Warming  and  ventilation.  10.  Light,  ir.  Dust.  12. 
Kitchen.  13.  House  hunting,  14.  Lessors,  lessees  and  their  liabili- 
ties, etc.  ^161  pages,  26  illustrations.  i2mo.,  cloth,  $1.00. 

Books  mailed  post-paid  to  any  address  on  receipt  of  price^ 


2l 


Metal  Plate  Work, 

ITS  PATTERNS  AND  THEIR  GEOMETRY. 

Also  Notes  on  Metals,  and  Rules  in  Mensuration;  for 
the  use  of  Tin,  Iron  and  Zinc-plate  Workers,  Copper- 
smiths, Boiler-makers,  Plumbers  and  others. 

By  C.  T.  MILLIS,  M.I.M.E. 


Second  Edition,  Revised  and  considerably  Enlarged. 


In  producing  the  Second  Edition  of  this  hook,  which  unfortunately 
has  been  long  delayed  through  pressure  of  work,  the  author  feels  con- 
fident that  the  addition  of  the  seventy  pages  of  new  matter  will  add 
considerably  to  the  value  of-  this  work,  besides  bringing  it  well  up  to 
date.  It  has  been  his  aim  throughout  this  work  to  be  as  plain  and 
practical  as  possible  and  to  be  a guide  and  workshop  companion  not  only 
to  the  young  mechanic  but  also  a valuable  help  to  the  old  and  experiencod 
worker  in  metal-plate.  The  number  of  illustrations  used  makes  this 
work  very  comprehensive  and  explicit. 


CONTENTS  OF  CHAPTERS. 

Classification.  Introductory  problems.  Articles  of  equal  taper  or 
inclination  of  slant.  Patterns  for  round  articles  of  equal  taper  or  inclina- 
tion of  slant.  Equal  tapering  bodies  and  their  plans.  Patterns  for  flat 
faced  equal  tapering  bodies.  Patterns  for  equal  tapering  bodies  of  flat 
and  curved  surfaces  combined.  Patterns  for  round  articles  of  unequal 
taper  or  inclination  of  slant.  Unequal  tapering  bodies  and  their  plans. 
Patterns  for  flat  faced  unequal  tapering  bodies.  Patterns  for  unequal 
tapering  bodies  of  flat  and  curved  surfaces  combined.  Patterns  for 
miscellaneous  articles.  Metals;  alloys;  solders;  soldering  fluxes.  Seams 
or  joints.  Useful  rules  in  mensuration  ; tables  of  weights  of  metals. 

Index.  377  pages,  314  illustrations,  12mo.,  cloth,  $3.50. 


22 


PIOMENTS,  PAINT 


AND 

PAIWTING- 

—BY— 

GEORGE  TERRY. 


Contents  of  Chapters. 

I.  Preliminary — Color,  pigments.  2.  Blacks.— General,  animal, 
bone,  Frankfort,  ivory,  lamp  ; Unimportant  blacks, — aniline,  candle, 
charcoal,  coal,  cork,  German,  iron,  lead,  manganese,  Prussian,  prus- 
siate,  Spanish,  tannin.  3.  Blues- — Cobalt,  Coeruleum.  copper,  Bre- 
men, Caeruleum,  smalts,  lime,  azurite,  Peligot,  verditer,  indigo, 
manganese,  Prussian,  yellow  prussiate,  Antwerp,  Bong’s,  Brunswick, 
Chinese,  Paris,  Saxon,  soluble,  Turnbull’s,  ultramarine.  4.  Browns. — 
Asphalt,  bistre,  bone,  Cappagh,  Cassel  earth,  chicory.  Cologne,  man- 
ganese, mars,  Prussian,  Rubens,  sepia,  ulmin,  umbers,  Vandyke. 
5.  Greens. — Baryta,  Bremen,  Brighton,  Brunswick,  Chinese,  chrome, 
cobalt,  Douglas,  emerald,  Guidnet’s,  Lokao,  malachite,  manganese, 
mineral,  mitis,  mountain,  Paris,  Prussian,  Rinmann,  sap,  Scheele’s, 
Schweinfurth,  terre  verte,  titanium,  verdigris,  verditer,  Verona 
earth,  Victoria,  Vienna,  zinc.  6.  Reds.  — Antimony,  Vermilion, 
baryta,  Cassius  purple,  Chinese,  chrome  orange,  chrome,  cobalt, 
cobalt  pink,  colcothar,  Derby,  Indian,  lead,  minium,  oxide,  Persian, 
Realgar,  red  lead,  rouge.  Venetian,  vermilion.  Victoria.  7.  Whites. — 
baryta,  blanc  fixe,  Charlton,  China,  clay,  enamelled,  English,  gyp- 
sum, white  lead,  lime,  lithophone,  magnesite,  mineral,  Orr’s  enamel, 
Paris,  permanent,  satin,  Spanish,  strontia,  terra  alba,  whiting,  zinc. 
8.  Yellows. — Arsenic,  aureolin,  cadmium,  chrome,  gamboge,  king’s, 
Naples,  ochres,  orpiment,  realgar,  siennas.  9.  Lakes. — Brazil-wood, 
carminated,  carmine,  cochineal,  madder,  yellow.  10.  Luminous 
Paint.  II.  Examination  of  Figments. — Fineness,  body  or  covering 
power,  color,  durability.  12.  Vehicles  and  Dryers. — Generalities. 
Oils, — ground-nut,  hempseed,  candle  nut,  linseed,  menhaden,  poppy- 
seed, tobacco-seed,  walnut,  wood  or  tung,  extraction  of  seed  oils,  dry- 
ers, litharge,  cobalt  and  manganese  benzoates,  cobalt  and  manganese 
borates,  resinates,  zumatic  dryers,  manganese  oxide,  Guynemer’s 
dryer,  l)oiled  oil,  manganese  oxalate.  13.  Paint  Machinery.  14. 
Painting. — The  surface,  priming,  drying,  filling,  coats,  brushes, 
water  colors,  discoloration,  composition,  area  covered,  measuring, 
carriage  and  car  painting,  woodwork  painting,  iron  painting,  fresco 
painting,  removing  odor.  Index. 

392  Pages,  49  Illustrations,  i2mo.,  Cloth,  $3.00. 


23 


THE  PRACTICAL 

POLISH  & VARNISH  MAKER. 

A TREATISE 

CONTAINING  750  PRACTICAL  RECIPES  AND  FORMULJl, 

FOR  THE  MANUFACTURE  OF 

Polishes,  Lacquers,  Varnishes  and  Japans,  of  all  kinds,  for 
Workers  in  Wood  and  Metal,  and  Directions  for  Using. 

By  H.  C.  standage. 


o 

The  purport  of  this  book  is  to  put  into  the  skilled  mechanics’  and 
amateurs’  hands  the  means  whereby  they  can  readily  prepare  their  own 
polishes,  varnishes,  lacquers  and  japans. 

CONTF.NTS. 

Ingredients  used  in  making  polishes,  lacquers,  varnishes  and  japans.  Directions  for 
the  filtering  and  bleaching  of  volatile  varnishes  and  lacquers.  Formulas  for  preparing 
polishes  for  wood.  Formulas  for  polishing  pastes,  creams’  and  renovators,  &c.  ; for 
furniture  creams  or  French  polishes  ; for  furniture  oils.  Revivers  and  renovators. 
Polishing  agents  for  metals.  Miscellaneous  polishing  compounds.  Practical  directions 
for  polishing  wood.  Directions  for  repolishing.  Processes  for  polishing  furniture. 
To  polish  delicate  cabinet  and  papier-mache  work.  To  polish  woods  in  the  lathe.  To 
renovate  old  furniture.  A durable  polish  for  ebony.  To  polish  walnut.  Waterproof 
finish  for  veneering.  Wood  finish.  Wax  polishing  of  floors.  Polishing  deal.  To  polish 
ebony.  To  put  onegg  shell  irolish  on  wood.  Polishing  black  woodwork.  Polishing 
black  and  gold  work.  Polishing  white  and  gold  work.  Dry  shining.  A good  polish  for 
walking  canes  and  other  hard  wood.  Water  polish.  Formulae  forpolishing  various  metals 
and  miscellaneous  materials.  To  polish  alabaster.  To  polish  book-edges.  To  polish 
cellnloid.  Friction  polish.  To  polish  bone,  horn,  ivory,  marble  and  imitation  marble. 
Formula  for  marble  dressing  or  polish.  To  jrolish — a black  marble  clock, -irearl,  piano 
keys,  plaster  of  Paris  work,  quartz,  shells,  show  cases,  slate  and  vulcanite.  To  clean 
and  xjolish  silverware.  Compoiind  for  waxing  and  polishing  floors.  Formulae  for  pre- 
paring lacquers  for  wood,  metal,  and  other  materials,  and  juethods  of  using  same. 
Lacquers  for  commoner  metals,  and  methods  of  lacquering  them.  Lacquering  metallic 
surfaces.  Varnishes  and  japans.  Formiilae  for  producing  volatile  and  fat  varnishes. 
General  notes  concerning  varnishes.  Varnishes  for  woodwork  in  general.  Special  and 
miscellaneous  varnishes.  Varnishes  for  boots,  shoes  and  leather.  Mastic  varnishes. 
Photographic  varnishes.  Varnishes  for  vioUns.  Caoutchouc  varnishes.  Oil  of  txirpen- 
tine  varnishes.  Formulae  for  making,  and  lorocesses  of  using,  japans  for  wood  and 
metal.  AVith  complete  index. 

260  PAGES,  I2MO.,  CLOTH,  PRICE  $2,50. 

24 


A F^RA.CXlCA.Iv  TTRE:AXISE) 

ON  THE 

STRENGTH  OF  RIRTERIHLS. 

INCLUDING  THEIR 

Elasticity  and  Resistance  to  Impact. 

By  THOMAS  BOX. 

Third  Edition. 

SYNOPSIS  OF  CONTENTS. 

Tensile  Strain.— Rivited  Joints. — Strength  of  punched  and  drilled 
plates,  principles  of  riveting,  riveted  joints  for  girder  work,  chain 
riveting,  steel  joints  for  girder  work,  strength  of  steel  rivets,  space 
between  rivets.  Cohesion  Applied  to  Pipes, — Strength  of  thin  two 
lap  welded  tubes,  general  rules  for  boilers,  boilers  for  very  high 
pressures,  factor  of  safety  for  boilers,  rules  for  strength  of  thick 
pipes,  tensile  strength  of  thick  cast  iron.  Strength  of  Chains,  Ropes, 
Etc.  Shearing  Strain. — Crushing  Strain.— Strength  of  Pillars 
— Theory  of  pillars,  rules  for  cast  iron,  wrought  iron  and  steel  pillars 
of  hollow,  cylindrical,  square,  rectangular,  X.  L,  and  channel  sec- 
tions. connecting  rods,  piston  rods,  and  radius  rods  for  steam  engines; 
effects  of  incipient  crushing  and  wrinkling.  Connection  of  Pillars 
WITH  Transverse  Strains. — Theoretical  strenght  of  cast  iron, 
wrought  iron,  steel  and  timber  pillars.  Wrinkling  Strain. — Trans- 
verse Stp.ain. — General  rules,  special  rules  for  beams  of  various  sec- 
tions, cast  iron  and  steel  beams,  plate  iron  and  lattice  girders,  tubular 
beam.s.  “Similar”  Beams — Examples  of  simnlar  beams,  general 
laws,  ‘ ‘unit”  girders.  Connection  of  T ransverse  and  other  Strains. 
— Roofs  — Strains  on  roofs,  strength  of  rafters,  struts,  tie-rods,  keys, 
rivets,  etc.,  curved  roofs.  Torsional  Strain. — Theoretical  laws, 
practical  rules  for  torsional  strength,  shafting  for  ordinary  machin- 
ery, marine  engine  shafts.  Extension  and  Compression. — General 
statement  of  facts,  cast  iron,  wrought  iron,  timber.  Deflection  ok 
Beams. — Form  of  curves  of  flexure,  general  rules  for  deflections, 
effects  of  modes  of  loading  and  section  of  beams,  deflection  with  safe 
load.  Torsional  Elasticity  — Modulus  of  Elasticity. — Permanent 
set,  defect  of  elasticity  manifested  by  set,  wrought  iron.  Impact. — 
Resistance  of  beams,  effect  of  inertia  of  beams,  resistance  as  the 
weight  of  beam  simply,  high  ratio  of  safe  and  breaking  loads,  sum- 
mary of  remarkable  laws.  Collapse  OF  Tubes. — Factor  of  Sakety. 
Proof  strain,  determination  of  factor  by  test  bars.  Fatigue  of 
Materials. — General  principles,  statical  and  Dynamic  Fatigue.  Ap- 
pendix. Index. 

525  Pages,  27  Full  Page  and  Folding  Plates,  8vo.,  cloth,  $7.25. 


25 


Graphic  Statics,  Geometry,  Drawing. 


Ortliosfrapliic  Projection. — An  Elementary  Treatise  on 
Orthographic  Projection  ; being  a New  Method  of  Teaching  the 
Science  of  Mechanical  and  Engineering  Drawing.  Intended  for  the 
Instruction  of  Engineers,  Architects,  Builders,  Smiths,  Masons,  and 
Bricklayers,  and  for  the  Use  of  Schools.  By  W.  Binns,  C E.  130 
pages,  60  illustrations,  23  large  folding  plates,  8vo.,  cloth.  $3.50 

Ditto. — Second  Course,  with  some  Practical  Remarks  on 
The  Teeth  of  Wheels,  The  Projection  of  Shadows,  Principles  of 
Shading,  and  Drawing  from  Machinery.  For  the  Instruction  of  En- 
gineers, Architects,  Builders,  Masons  and  for  the  Use  of  Science 
Schools  and  Classes.  By  W.  Binns,  C.E.  180  pages.  67  illustra- 
tions, 23  plates  and  tables,  8vo.,  cloth.  l4*5o 

Xlic  Klcmcnts  of  Orapliic  Statics*  By  Carl  Von 
Ott.  Translated  from  the  German  by  G.  Sydenham  Clarke.  Con- 
tents : — Part  I. — Composition  of  Forces.  The  Simple  Beam.  Reso- 
lution of  Forces.  Interior  Forces  of  Stresses.  Part  II. — Braced 
Structures.  Stress  Diagram.  Braced  Beams,  with  Travelling 
Loads.  The  Arch.  Part  3.  — Elements  of  the  Theory  of  Strength 
of  Materials.  121  pages,  93  illustrations,  i2mo.,  cloth.  |i.5oj:. 

Xlic  Principles  of  Orapbic  Statics.— By  Major  G.  S. 
Clarke.  Contents  of  Chapters,  i. — Graphic  Arithmetic.  2. — Com- 
position and  Resolution  of  Forces,  etc.;  Parallel  Forces;  Moments  of 
Forces;  Couples.  3. — Reciprocal  Figures.  4. — Stress  Diagrams.  5. — 
Action  of  Stationary  Loads;  Beams  Fixed  at  One  End;  Beams  Support- 
ed at  Both  Ends.  6. — Travelling  Load.  7. — Braced  Girders.  8. — Cen- 
tre of  Parallel  Forces;  Centre  of  Gravity.  9. — Moment  of  Inertia; 
Central  Ellipse,  etc.  10. — Moment  of  Resistance;  Central  Ellipse, 
etc.  Appendix.  Tables.  142  pages,  1 18  illustrations  and  ii  plates, 
4to.,  cloth.  $5.00 

Practical  Ocometry. — Perspective  and  Engineering  Draw- 
ing. By  G.  S.  Clarke.  Chapter  i. — Plain  Geometry.  Solid  Geo- 
metry, 2. — Orthographic  Projection.  3. — Lines  and  Planes.  4. — The 
Use  of  Indices.  5. — The  Projection  of  Solids.  6.  —Sections  of  Solids 
by  Planes.  7. — Inter-penetration  of  Solids.  8.— Tangent  Planes  to 
Surfaces.  9.  — Determination  of  Shadows.  10.  — Shade-lines 
and  Shadings.  ii. — Isometric  Projection.  12. — Perspective;  En- 

gineering Drawings.  13. — General  Considerations  and  Rules.  14. — 
Selection  of  Drawing  Instruments,  etc.  Vol.  i.  Text,  175  pages, 
102  illustrations,  8vo.,  cloth.  Vol.  2. — Plates,  98  illustrations,  4to, 
cloth.  Two  vol’s  complete,  $4.00 

Books  mailed  post-paid  to  any  part  of  the  World  on  receipt  of  price. 


2t> 


TTME 

Commercial  Organization  of  Factories. 


A Handbook  for  the  use  of  Manufacturers,  Directors,  Auditors, 
Engineers,  Managers,  Secretaries,  Accountants,  Cashiers, 
Estimate  Clerks,  Prime  Cost  Clerks,  Bookkeepers, 
Draughtsmen,  Students,  Pupils,  &c.,  &c. 

By  J.  SLATER  LEWIS. 


“The  system  of  accounts  presented  in  this  book  is  the  result  of  many 
years  close  observation  and  practical  experience,  and  is,  what  may  be 
termed  an  interlocking  system,  under  which  each  and  every  account 
in  a factory  is  brought  into  line  monthly,  and  a general  balance  of 
the  whole  affected.  It  will  be  seen  from  an  inspection  of  the  dia- 
grams A and  B,  that  the  system  is  not  only  capable  of  diagrammatic 
proof,  and  may,  therefore  be  relied  upon  as  being  complete  ; but  that 
it  may  be  expanded  or  contracted  as  circumstances  may  require.” 


Stock  Requisition-Note  Guard-Book,  eight  pages  of  diagrams,  large 
oblong.  A large  diagram  of  Manufacturing  Accounts,  i8q6,  colored, 
19^  X 27i  inches.  A large  diagram  of  Balance  Sheets,  1896,  colored, 
20  X 2yi  inches.  Large  Folding  plate  Diagram  of  Manufacturers’ 
Accounts,  1896,  colored.  Folding  plate.  Staff  Organization  Diagram, 
192  illustrations,  diagrams,  forms,  orders,  receipts,  records,  &c. 
Contracts  and  estimates.  Travellers’ order  forms.  Bills  of  Exchange, 
&c.,  &c.  Very  full  index.  540  pages,  4to.,  cloth,  $ 12.00 


CONT'EKTTS  OK  CK[A.KXKR.S. 

Introduction,  i. — The  Directors.  2. — The  Manager.  3. — The  Secretary.  4. — The 
Auditor.  5. — The  Accountant.  6.— The  Cashier.  7 —Correspondence  Clerk.  8.— Sup- 
plies’ Orders  and  Invoices.  9. — Customers’  Orders  and  Invoices.  lo. — Drawing  Office. 
II.— Estimating.  12. — Stationery.  13. — Advertising  and  Catalogues.  14. — The  Works. 
Manager.  15. — The  Inspector.  16. — The  Entrance  Gates  and  the  Gatekeeper.  17. — 
The  Stores  and  Storekeeper.  18. — The  Warehouse  and  Warehouseman.  19 — Carriage 
20. — The  Eoremen.  21. — The  Time-keeper  and  Job  Clerk.  22. — The  Paying  of  Wages. 
23. — Establishment  Charges.  24. — Stock  Surveys.  25. — Diagrams  and  Curves.  26. — 
Diagrams  of  Manufacturing  Accounts  and  Balance  Sheets.  27. — General  View  of 
Manufacturing  Accounts.  28. — Synopsis  of  Transactions  Relating  to  Purchases  and  Stores. 
29. — Synopsis  of  Transactions  Relating  to  Labor  and  Time.  30. — Synopsis  of  Transactions 
Relating  to  Manufacturing  and  Prime  Costs.  3T. — Synopsis  of  Transactions  Relating  to 
Warehouse,  Stock  and  Sales.  32. — Commercial  Office  ( Orders  and  Invoices.)  3^  — Stores. 
34.— Works  and  Job  Office.  35. — Warehouse.  36.— Prime  Cost  and  Ledger  Clerk’s  Office. 
37. — Balancing  and  Accounts.  38. — The  Depreciation  of  Plant  and  Buildings.  39 —Re- 
cording Plant  and  Buildings.  40.— Foundry  Accounts  41. — Forge  Accounts.  42. — Pat- 
tern Shop  Accounts.  43. — Salaries  and  Expenses.  44. — Agents  and  Travelers.  45. — 
Pupils.  46.— Apprentices.  47.— Shipping,  48,— Samples,  Patterns,  &c.  49.— Miscellane- 
oas.  Appendix.  Index. 


37 


Books  by  P.  L.  Simmonds. 


TTropical  Agriculture.  A treatise  on  the  culture,  pre- 
paration. commerce  and  consumption  of  the  principal  products  of  the 
vegetable  kingdom. 

Section  i. — Plants  yielding  seeds,  leaves  and  other  substances  em- 
ployed in  domestic  use  for  the  preparation  of  dietetic  beverages,  etc.: 
Cacas,  guarana,  kola  nuts,  coffee,  tea,  Yerba  Mate,  sugar,  maple 
sugar,  palm  sugar,  beetroot  sugar,  glucose  or  starch  sugar,  sorghum 
sugar,  maize  sugar.  Section  2. — The  useful  plants  and  their  eco- 
nomic products  ; Coconut  palm,  African  oil  palm,  gomuti  palm,  wild 
date  palm  (India),  Palmyra  palm,  sago  palm,  bastard  sago,  Carnauba 
palm  (Brazil),  betelnut  palm,  betel  pepper  leaf,  date  palm,  spiny  date 
(Africa),  wine  or  bamboo  palm.  Doum  palm  (Egypt),  dwarf  palm.  Sec. 
3. — The  tropical  serials  and  starch-producing  plants  : Indian  maize 
rice,  millets,  sugar  millet,  broom  corn,  panicums,  Italian  millet,  In- 
dian millet,  shamay,  sawa  millet,  cumboo  or  spiked,  raggee,  koda 
millet.  Starch-producing  plants. — Arrowroot,  Tacca  plant,  Manioc  or 
Cassava  starch,  the  sweet  potato,  the  yam  tribe,  the  coco  or  eddoe, 
Japanese  starches,  chayote,  potato  starch  and  maize  starch.  Sec- 
tion 4. — The  Principal  Vegetable  Dye  Stuffs  of  Commerce. — 
Madder,  munjeet,  chay  root,  safflower,  saffron,  turmeric,  cutch, 
gambier,  annotta.  Henna,  alkanet  root.  Section  5. — The  Oil  Seeds 
AND  Vegetable  Oils  of  Commerce. — Olive,  linseed,  ground  nut,  cot- 
ton seed,  castor  oil  plant,  rape,  mustard,  curdee,  sesame,  niger,  Ca- 
melina,  sunflower,  candle  nut,  Japan  wax,  poppyseed,  melon,  physic 
nut,  croton  oil,  Chinese  oils,  oil  of  Ben,  essential  oils.  Section  6. — 
The  Principal  Fruits  OF  Commerce. — Vine  culture  and  the  grape; 
dried  fruits;  products  of  the  orange  family  ; pineapples,  plantain, 
banana,  fig,  its  culture  and  commerce,  and  other  fruits.  Seceion  7’ 
— The  Spices  of  Commerce. — Pepper,  chillies,  ginger,  nutmegs, 
mace,  spice  barks,  cinnamon,  vanilla,  pimento,  cloves,  cardamoms’ 
Section  8. — Tobacco:  Its  production,  uses  and  commerce.  Index, 
539  pages,  8vo,  cloth.  $8.oo| 

A Dictionary  of  Useful  Animals  and  their  products. 
A manual  of  ready  reference  for  all  those  which  are  commercially 
important,  and  others  which  man  has  utilized.  Including  a glossary 
of  trade  and  technical  terms.  136  pages,  i6mo,  cloth,  80  cts. 

Xlae  Animal  Food  Kesources  of  Dilferent  Na- 
tionSy  with  mention  of  some  of  the  special  dainties  of  various  peo- 
ple, derived  from  the  animal  kingdom.  461  pages,  i2mo,  cloth,  $1.00. 

MopSf  their  cultivation,  commerce  and  uses  in  various  countries. 
A manual  of  reference  for  the  grower,  dealer  and  brewer.  Contents 
of  Chapters. — i. — History,  botany,  chemistry,  2. — Medical  uses. 
3. — Systems  of  cultivation.  4. — Cultivation.  5. — Qualities.  6. — 

Cultivation  in  Europe.  7. — Production  in  U.  S.  8. — Culture  in 
Australasia,  g. — Bitter  substitutes  which  have  been  used  for  the  Hop, 
etc,  " 135  pages  with  tables,  i2mo.  cloth,  $1.25! 


Xhe  Gras  Engineer’s 

LABORATORY  HANDBOOK. 

BY  JOHN  HORNBY,  F.LG. 


Synopsis  of  Contents. 

Introdnctor j’' : — The  balance  ; weights  and  weighing.  Sampling - 
mechanical  division  ; drying  and  dessicaiing  ; solution  and  evapora; 
tion  ; precipitation  ; filtration  and  treatment  of  precipitates  ; simple 
gravimetric  estimates.  Volumetric  Analysis — Notes  on  the  pre- 
paration of  solutions.  Indicators  used  in  the  volumetric  estimation 
of  acids  and  alkalis.  Analysis  by  saturation.  (Alkalimetry  and 
acidimetry.)  Preparation  of  normal  acid  and  alkaline  solutions. 
Processes  of  oxidation  and  reduction.  Special  Analyses  E-equired 
in  Gasworks. — Analysis  of  coal  and  coke.  Estimation  of  the  im- 
purities in  crude  gas.  Testing  purified  gas  for  sulphur  compounds, 
etc.  Analysis  of  ammoniacal  liquor.  Analysis  of  li'me.  Analysis  of 
limestone.  Analysis  of  oxide  of  iron.  Analysis  of  spent  oxide  of 
iron.  Analysis  of  fire  clay  and  fire-bricks.  Assay  of  coal  tar.  Frac- 
tional distillation.  Determination  of  the  specihc  gravity  of  gas. 
Teclinical  Gas  Analysis.  - Notes  on  the  measurement  of  gases. 
Calibration  of  measuring  tubes.  The  Hempel  Burette.  Hempel’s 
gas  apoaratus.  Double  absorption  pipette.  Appendix.— Gas  re- 
feree's instructions.  Time  and  mode  of  testing  for  purity.  Meters. 
Cubic  foot  measure,  etc.  Index.  304  pages,  03  illustrations  and  36 
pages  of  tables,  lemo.,  cloth,  I2.30. 


PRACTICAL  HINTS  ON  THE  CONSTRUCTION 

— AND— 

WORKING  OF  REGENERATOR  FURNACES. 

BY  MAURICE  GRAHAM,  C.  E. 

Contents. 

Material. — Fire-clay,  fire-brick,  retorts,  cement,  mortar,  hydraulic 
mortar,  cement  mortar,  concrete,  common  brick,  wrought  iron,  cast- 
iron.  Gas-tight  joints.  Retort  mouthpieces  and  lids.  Furnaces  and 
settings. — Foundations,  footings,  main  piers,  centering.  Approx- 
imate rules  for  the  thickness  of  arches  and  abutments.  Chimney 
shafts.  The  producer.  Air  boxes.  Regenerators.  Analysis  of 
producer  gases  before  combustion.  Analysis  of  water  products  in 
main  flue.  Fuel  experiments.  Bad  heats.  Summary.  Advantages 
claimed  on  behalf  of  the  gaseous  firing  system.  Index.  131  pages, 
50  illustrations,  i6mo.,  liuip  leather.  $1.2^. 


2g 


A PRACTICAL  TREATISE  CN 


As  Applied  to  the  Useful  Arts  for  the  Use  of  Engineers ^ Architects^  etc. 

BY  XMOMAS  BOX, 


CONTENTS  OF  CHAPTERS. 

I.  General  Principles  and  Data.— Unit  of  Heat ; Specific  Heat  of— Solids 
and  Liquids,  Air  and  Gases  ; Liquefaction,  Latent  Heat  of ; Ebulition;  Latent 
Heat  of  Vaporization  ; Expansion  of  Solids  : Contraction  of  Metals  in — Casting, 
Wrought  Iron  ; Expansion  of — Liquids,  Gases,  Moist  Air ; Thermometers ; 
Temperature  of  the  Globe  ; Sources  of  Heat  and  Cold  ; Heat  Developed  by— 
Friction,  Compression;  Frigorific  Mixtures;  Density  and  Weight  of  Bodies; 
Atomic  Weight  of  Bodies.  II.  On  Combustion. — Theory  of  Combustion ; Heat 
Evolved  in  Combustion  by — Theory,  Experiment ; Air  required  for  Combus- 
tion ; Products  of  Combustion  ; Modes  of  giving  out  Heat  usefully ; Tempera- 
ture of  Air  in  Furnaces ; Means  of  obtaining  veiy  High  Temperatures ; Radia- 
ting Power  of  Combustibles ; Combustion  with  Steam  Boilers ; Relative  effect 
of  Long  and  Short  Boilers ; Effect  of  Forcing  the  Fire  ; Effect  of  too  much  Air ; 
Effect  of  too  little  Air.  HI.  On  Steam  Boilers. — Effective  Heating  Surface; 
Power  of  Boilers ; Boilers  for  Steam  Engines ; Expansive  Steam ; Water  Heat- 
ers ; Superheating  Steam ; Furnaces  to  Steam  Boilers ; Fire-bars ; Safety- 
valves;  Dampers;  Area  and  Arrangement  of  Flues;  Strength  of — Steam 
Boilers,  Boiler  Tubes.  IV.  On  the  Efflux  of  Air,  Etc,— Analogy  of  Efflux 
of  Water;  Velocity  of  Air,  etc.— into  a Vacuum,  into  Air;  Coefficient  of  Con- 
tractions ; Friction  of  Long  Pipes ; Square  and  Rectangular  Channels , Effect 
of  Repeated  Enlargements  and  Contractions;  Discharge  of  Steam;  Steam- 
pipes  to  Engines.  V.  On  Chimneys. — Chimneys  to  Steam-boilers;  Round 
Chimneys ; Square  Chimneys ; Effect  of — Long  and  Short  Flues,  Internal  Tem- 
perature. VI.  On  Vapors. — Elastic  Force  of  Vapor;  Mixtures  of  Vapor  and 
Air  ; Vapor  in  the  Atmosphere  ; Hygrometry ; Steam,  Elastic  Force  of ; Elastic 
Force  of  Vapor  of  Alcohol,  etc.  VII.  On  Evaporation. — Evaporation  in  Open 
Air  ; Effect  of  Wind  on  Evaporation  ; Cold  Produced  by  Evaporation  ; Evapor- 
ation at  High  Temperatures ; Evaporating  Pans ; Refrigerators ; Condensation 
Reservoirs  to  Steam-engines ; Dryness  of  Air,  increased  by  Heat ; Evaporating 
Vessels  for  Stoves ; Evaporation  at  Boiling  Point.  VIII.  On  Distillation. — 
Principles  of  Distillation  ; Condensing  Apparatus.  IX.  ON  Drying. — Drying — 
in  Open  Air,  by  Heated  Air ; Proper  Position  of  Inlet  and  Outlet  Openings ; 
Drying— Closet  for  Linen,  for  Asylums,  etc.,  at  High  Temperatures,  in  Closed 
Room,  by  Drying  Cylinders.  X.  ON  Heating  Liquids. — Heating  Liquids  by — 
Fire  Direct,  Steam,  at  the  top,  Gas,  Petroleum,  etc.  XI.  On  Heating  Air, — 
Heating  Air — Principles  of,  by  Stoves;  Heating  by — Horizontal  Flue-pipes, 
Vertical,  Steam-pipes,  Enclosed  Pipes;  Air-cocks;  Apparatus  for  Condensed 
Water  ; Expansion  of  Steam-pipes,  etc.;  Heating  Air  by  Hot-water  Pipes  ; Ve- 
locity necessary  to  renew  the  neat';  Position  of  the  Fire.  XII.  On  THE  TRANS- 
MISSION OF  Heat  and  Laws  of  Cooling.— Loss  of  Heat  by— Radiation,  Con- 
tact of  Air,  Conduction,  Buildings,  Walls,  Glass  in  Windows,  Glasshouses; 
Effect  of  Covers  on  Cooling ; XIII.  Laws  of  Cooling  at  High  Tempera- 
tures.— Loss  by — Radiation,  Dulong’s  Formula,  Contact  of  Air,  Dulong’s  For- 
mula, Steam-Pipes,  Enclosed  Steam-pipes,  Polished  Metal  Surfaces,  etc..  Thick 
Cast-iron  Pipes,  Steam-pipes,  cased.  XIV.  ON  Ventilation. — Respiration; 
Air  required  for — Respiration,  Carrying  off  Vapor,  Exhalations,  Carrying  off 
Animal  Heat,  Lighting  Apparatus;  Methods  of  effecting  Ventilation  : Sufnmer 
and  Winter  Ventilation;  Mechanical  Ventilation;  Ventilation  ot— Schools, 
Chapels,  Hospitals;  Effect  of  different  Combustibles  in  Ventilation.  XV.  Ex- 
amples OF  Buildings  Heated  and  Ventilated.— Prison  Mazas ; Prison  of 
Provins;  Church  of  St.  Roch — Particulars  of.  Temperature  of  Walls,  Volume 
of  Air,  Time  to  Heat  Building,  Time  to  Cool  Building,  Heating  Apparatus. 
XVI.  On  Wind,  and  its  Effects  on  Ventilation,  etc.— Influence  of  Wind 
on  Ventilation  ; Force  and  Velocity  of  Wind;  Cowl  for  Chimneys;  Form  of 
Vane  for  Chimneys ; Stability  of  Buildings  in  Storms.  Appendix. — Explosive 
Force  of  Gases  ; Evaporation  at  Low  Pressures  of  Air  ; Absorption  of  Gases  by 
Liquids ; Ice-houses.  Index. 

300  pages,  14  plates,  120  tables,  i2mo.,  cloth,  $5.00, 


30 


STANDARD  MEASURES 

OF 

UNITED  STATES, 

GREAT  BRITAIN,  AND  FRANCE. 

BY 

ARTHUR  S.  C.  WURTELE,  Mem.  Amer.  Soc.  C.E., 

ASS’T  ENG..  N.  Y.  C.  & H.  R.  R. 

A history  of  Standard  Measures  from  their  introduction 
in  1736  by  the  Royal  Society  to  the  present  time,  with 
actual  comparisons  of  the  Measures  made  at  various  times 
in  the  United  States,  Great  Britain  and  France.  Origin  of 
the  Metre  and  comparative  results  according  to  Delamhre, 
Bessel,  Airy,  and  Clarke.  Tables  showing  the  reductions  of 
the  French  Toise  into  English  Feet,  Metre  in  Inches,  and 
length  of  the  Seconds  Pendulum  as  given  by  different  writers. 
Appendix  showing  the  disadvantages  in  practical  use  of  the 
Metrical  System,  and  the  inconvenience  attending  its  adoption, 

8 VO,  paper,  price  50  cents. 

SPON  & CHAMBERLAIN, 

PUBLISHERS,  IMPORTERS  AND  BOOKSELLERS, 

12  CORTLANDT  STREET,  NEW  YORK. 


31 


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Jeweiers,  Watch  and  Cloekmakers. 


Britten,  F.  J.  Former  Watch  and  Clock-makers  and  Their  Work, 
including  an  account  of  the  development  of  horological  instruments  from 
the  earliest  mechanism,  \vith  portraits  of  masters  of  the  art.  And  a directory 
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Watch  and  Clock-makers’  Hand-book,  Dictionary  and  Guide. 

A complete  description  and  explanations  of  all  technical  terms  used  in 
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Neltliropp,  Hev.  H.  Li.  A Treatise  on  Watch-work  Past  and 
Present.  310  pages,  75  illustrations,  121110,  cloth,  2.50 

CONTENTS. 

A watch,  definition  of  words  and  terms  used  in  watch-work,  tools  required 
for  watch- work,  time,  historical  summary  to  the  15th,  century,  from  A.  D. 
1500  to  the  present  time,  on  calculations  of  the  numbers  for  wheels  and 
pinions,  their  proportional  sizes,  trains,  etc.,  of  dial  work  or  motion  work, 
length  of  time  of  going  without  winding  up,  the  verge,  horizontal  or  cylinder 
watch,  the  duplex,  the  lever,  the  chronometer  or  detached  escapement, 
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pensation, jewelling  of  pivot-holes,  Clerkenwell,  fallacies  of  the  trade,  how 
to  choose  and  use  a w^atch,  conclusion,  appendix,  index. 

Kemlo,  F.  Watch  Repairers’  Hand-book.  Being  a complete  guide 
to  the  young  beginner  in  taking  apart,  putting  together,  and  thoroughly 
cleaning  the  English  lever  and  other  foreign  watches,  and  all  American 
watches.  By  F.  Kemlo,  practical  watch-maker.  93  pages,  6 illustrations, 
121110,  cloth,  1.25 

Immiscli,  Moritz.  Prize  Essay  on  the  Balance  Spring  and  its 
Isochronal  Adjustments.  50  pages,  i2mo,  cloth,  i.oo 

Kirkpatrick,  T.  S.  G.  Simple  Rules  for  the  Discrimination  of 
Gems.  20  pages,  121110,  French  calf,  .80 

CONTENTS. 

Specific  gravity,  crystalline  forms,  cleavages,  fracture,  lustre,  streak,  rule 
for  finding  specific  gravity,  scale  of  hardness,  curved  edge  of  diamond, 
color  of  stones,  valuable  stones  in  river  beds,  electric  test. 

‘Rowell,  Harvey.  Manual  of  Instruction  in  Hard  Soldering.  With 
an  appendix  on  the  repair  of  bicycle  frames,  notes  on  alloys,  and  a chapter 
on  soft  soldering.  Second  edition,  revised  and  enlarged,  66  pages,  illus- 
trated, 121110,  cloth,  .75 

See  also  Workshop  Receipts,  fifth  series,  2.00  each. 

Cromwell,  J.  A System  of  Easy  Letter.  Containing  26  pages  of 
al[)liabets  of  various  designs.  Oblong,  8vo,  paper  cover,  .50 

Bool’S  mailed  post  paid  to  any  address  on  receipt  of  published  price. 


32 


GETTY  CENTER  LIBRARY 

NH  510  T74  1897 
^ ^ Townsend. 

Chemistry  tor  photographers  / 


3 3125  00324 


CONS 

BKS 

Charles  F. 


0153 


